Synthesis and use of precursors for ALD of group VA element containing thin films

ABSTRACT

Atomic layer deposition (ALD) processes for forming Group VA element containing thin films, such as Sb, Sb—Te, Ge—Sb and Ge—Sb—Te thin films are provided, along with related compositions and structures. Sb precursors of the formula Sb(SiR 1 R 2 R 3 ) 3  are preferably used, wherein R 1 , R 2 , and R 3  are alkyl groups. As, Bi and P precursors are also described. Methods are also provided for synthesizing these Sb precursors. Methods are also provided for using the Sb thin films in phase change memory devices.

REFERENCE TO RELATED APPLICATIONS

The present application is the U.S. National Phase of InternationalApplication PCT/US2010/053982 filed Oct. 25, 2010 and claims priorityunder 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/255,055filed Oct. 26, 2009, U.S. Provisional Application No. 61/308,793 filedFeb. 26, 2010, and U.S. Provisional Application No. 61/383,143 filedSep. 15, 2010, each of which are hereby incorporated by reference intheir entirety.

PARTIES OF JOINT RESEARCH AGREEMENT

The invention claimed herein was made by, or on behalf of, and/or inconnection with a joint research agreement between the University ofHelsinki and ASM Microchemistry signed on Nov. 21, 2008. The agreementwas in effect on and before the date the claimed invention was made, andthe claimed invention was made as a result of activities undertakenwithin the scope of the agreement.

BACKGROUND

1. Field of the Invention

The present application relates generally to methods for forming thinfilms comprising Group VA elements (Sb, As, Bi, P, N) by atomic layerdeposition. Such films may find use, for example, in phase change memory(PCM) devices and in optical storage media.

2. Description of the Related Art

Thin films comprising group VA elements are used in many differentapplications, including, for example, non-volatile phase-change memories(PCM), solar cells, III-V compounds and optical storage materials. III-Vcompound semiconductors can be used in many different application areas,including transistors, optoelectronics and other application areas, forexample, in bipolar transistors, field effect transistors, lasers, IRdetectors, LEDs, wide band gap semiconductors, quantum well or quantumdot structures, solar cells and in monolithic microwave integratedcircuits. The operation of PCM cells is based on the resistivitydifference between amorphous and crystalline states of the activematerial. A resistivity difference of more than three orders ofmagnitude can be obtained by many different phase change alloys. Theswitching in a PCM cell is generally accomplished by heating thematerial locally with suitable current pulses, which, depending on theintensity of the pulse, leave the material in a crystalline or amorphousstate.

A wide variety of different PCM cell structures have been reported, manyof which use trench or pore-like structures. Sputtering has typicallybeen used in preparing PCM materials, but the more demanding cellstructures will require better conformality and more control of thedeposition process. Sputtering may be capable of forming simple pore andtrench structures, however, future PCM applications will require morecomplicated 3-D cell structures that cannot be formed using sputteringtechniques. Processes with greater precision and control, such as atomiclayer deposition (ALD), will be required to make these complicatedstructures. Using an atomic layer deposition process provides greaterprecision and control over the deposition, including better conformalityand better control of the composition of the deposited film.

Atomic layer deposition processes for depositing Sb-containing thinfilms have been limited, in part, by a lack of appropriate precursors.

A need exists, therefore, for methods for controllably and reliablyforming thin films of phase change materials comprising antimony by ALDfrom gas phase reactants.

SUMMARY OF THE INVENTION

The present application relates generally to methods for forming thinfilms comprising Group VA elements (Sb, As, Bi, P) by atomic layerdeposition.

Methods and compositions are also disclosed herein for synthesizingvarious antimony precursors comprising Sb(SiR¹R²R³)₃, wherein R¹, R²,and R³ are alkyl groups with one or more carbon atoms.

ALD methods are also disclosed herein for depositing thin filmscomprising antimony, along with related compositions and structures. Themethods generally comprise providing a pulse of a first vapor phasereactant into the reaction chamber to form no more than about a singlemolecular layer of the reactant on the substrate; removing excess firstreactant from the reaction chamber; providing a pulse of a second vaporphase reactant to the reaction chamber such that the second vapor phasereactant reacts with the first reactant on the substrate to form a Sbcontaining thin film wherein the second vapor phase reactant comprisesSb(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkyl groups with one or morecarbon atoms. In some embodiments the first reactant comprises antimony.In some embodiments the first reactant does not comprise oxygen.

Methods for forming Ge—Sb—Te thin films on a substrate in a reactionchamber by an ALD process are also disclosed herein. The methodsgenerally comprise a plurality of Sb deposition cycles, each cyclecomprising alternate and sequential pulses of a first precursor and asecond Sb precursor comprising Sb(SiR¹R²R³)₃, wherein R¹, R², and R³ arealkyl groups with one or more carbon atoms; a plurality of Te containingdeposition cycles, each cycle comprising alternate and sequential pulsesof a third precursor and a fourth precursor comprising Te; and aplurality of Ge containing deposition cycles, each cycle comprisingalternate and sequential pulses of a fifth precursor and a sixthprecursor comprising Ge.

Methods for forming Ge—Sb—Se thin films on a substrate in a reactionchamber by an ALD process are provided herein. The methods comprise aplurality of Sb deposition cycles, each cycle comprising alternate andsequential pulses of a first precursor and a second Sb precursorcomprising Sb(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkyl groups withone or more carbon atoms; a plurality of Se containing depositioncycles, each cycle comprising alternate and sequential pulses of a thirdprecursor and a fourth precursor comprising Se; and a plurality of Gecontaining deposition cycles, each cycle comprising alternate andsequential pulses of a fifth precursor and a sixth precursor comprisingGe.

Method for making Sb precursors are provided herein. The methodscomprise forming a first product by reacting a Group IA metal with acompound comprising Sb; and subsequently combining a second reactantcomprising R¹R²R³SiX with the first product, wherein R¹, R² and R³ arealkyl groups with one or more carbon atoms and X is a halogen atom,thereby forming a compound with the formula Sb(SiR¹R²R³)₃.

Methods for making precursors comprising a group VA element are providedherein. The methods comprise forming a first product by reacting a GroupIA metal with a compound comprising a group VA element; and subsequentlycombining a second reactant comprising R¹R²R³SiX with the first product,wherein R¹, R² and R³ are alkyl groups with one or more carbon atoms andX is a halogen atom, thereby forming a compound with the formulaL(SiR¹R²R³)₃, wherein L is the group VA element, wherein the group VAelement is As, Sb, Bi, N or P.

Methods for making precursors comprising a group VA element are providedherein. The methods comprise forming a first product by reacting a GroupIA metal with a compound comprising a group VA element; and subsequentlycombining a second reactant comprising R¹R²R³AX with the first product,wherein R¹, R² and R³ are alkyl groups with one or more carbon atoms, Ais Si, Sn, or Ge and X is a halogen atom, thereby forming group VAelement containing compound with the formula L(AR¹R²R³)₃, wherein L isthe group VA element, wherein the group VA element is As, Sb, Bi, or P.

Atomic layer deposition (ALD) processes for forming group VA elementcontaining thin film on a substrate in a reaction chamber are provideherein. The methods comprise a plurality of Group VA element depositioncycles, each cycle comprising: providing a pulse of a first vapor phasereactant into the reaction chamber to form no more than about a singlemolecular layer of the reactant on the substrate; removing excess firstreactant from the reaction chamber; providing a pulse of a second vaporphase reactant to the reaction chamber such that the second vapor phasereactant reacts with the first reactant on the substrate to form a groupVA element containing thin film wherein the second vapor phase reactantcomprises X(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkyl groups with oneor more carbon atoms and X is group VA element (Sb, As, Bi, P); andremoving excess second reactant and reaction byproducts, if any, fromthe reaction chamber.

Atomic layer deposition (ALD) processes for forming As-containing thinfilms on a substrate in a reaction chamber are provided herein. Themethods comprise a plurality of As deposition cycles, each cyclecomprising: providing a pulse of a first vapor phase reactant into thereaction chamber to form no more than about a single molecular layer ofthe reactant on the substrate; removing excess first reactant from thereaction chamber; providing a pulse of a second vapor phase reactant tothe reaction chamber such that the second vapor phase reactant reactswith the first reactant on the substrate to form a As containing thinfilm, wherein the second vapor phase reactant comprises As(SiR¹R²R³)₃,and wherein R¹, R², and R³ are alkyl groups with one or more carbonatoms; and removing excess second reactant and reaction byproducts, ifany, from the reaction chamber.

Atomic layer deposition (ALD) processes for forming Sb-containing thinfilms on a substrate in a reaction chamber are provided herein. Themethods comprise a plurality of Sb deposition cycles, each cyclecomprising: providing a pulse of a first vapor phase reactant into thereaction chamber to form no more than about a single molecular layer ofthe reactant on the substrate; removing excess first reactant from thereaction chamber; providing a pulse of a second vapor phase reactant tothe reaction chamber such that the second vapor phase reactant reactswith the first reactant on the substrate to form a Sb containing thinfilm wherein the second vapor phase reactant comprises Sb(GeR¹R²R³)₃,wherein R¹, R², and R³ are alkyl groups with one or more carbon atoms;and removing excess second reactant and reaction byproducts, if any,from the reaction chamber.

Atomic layer deposition (ALD) processes for forming group VA elementcontaining thin films on a substrate in a reaction chamber are providedherein. The methods comprise a plurality of Group VA element depositioncycles, each cycle comprising: providing a pulse of a first vapor phasereactant into the reaction chamber to form no more than about a singlemolecular layer of the reactant on the substrate; removing excess firstreactant from the reaction chamber; providing a pulse of a second vaporphase reactant to the reaction chamber such that the second vapor phasereactant reacts with the first reactant on the substrate to form a groupVA element containing thin film wherein the second vapor phase reactantcomprises a group VA atom that is bonded to one or more of Si, Ge, or Snand wherein the group VA element is Sb, As, Bi or P; and removing excesssecond reactant and reaction byproducts, if any, from the reactionchamber.

Atomic layer deposition (ALD) processes for forming thin filmscomprising a group VA element on a substrate in a reaction chamber areprovided herein. The processes comprise a plurality of Group VA elementdeposition cycles, each cycle comprising: providing a pulse of a firstvapor phase reactant into the reaction chamber to form no more thanabout a single molecular layer of the reactant on the substrate;removing excess first reactant from the reaction chamber; providing apulse of a second vapor phase reactant to the reaction chamber such thatthe second vapor phase reactant reacts with the first reactant on thesubstrate to form a thin film comprising a group VA element, wherein thesecond vapor phase reactant comprises a group VA atom that is bonded toone or more of Si, Ge, or Sn, wherein the group VA element is Sb, As,Bi, N, or P, and wherein the first vapor phase reactant does notcomprise a transition metal, Si, or Ge when the group VA atom in thesecond vapor phase reactant is N; and removing excess second reactantand reaction byproducts, if any, from the reaction chamber.

Atomic layer deposition (ALD) processes for forming nitrogen-containingthin films on a substrate in a reaction chamber are provided herein. Theprocesses comprise a plurality of deposition cycles, each cyclecomprising: providing a pulse of a first vapor phase reactant into thereaction chamber to form no more than about a single molecular layer ofthe reactant on the substrate, wherein the first vapor phase reactantdoes not comprise transition metal; removing excess first reactant fromthe reaction chamber; providing a pulse of a second vapor phase reactantto the reaction chamber such that the second vapor phase reactant reactswith the first reactant on the substrate to form a nitrogen containingthin film, wherein the second vapor phase reactant comprisesN(AR¹R²R³)_(x)R_(3−x), and wherein x is from 1 to 3, A is Si, Ge or Sn,and R, R¹, R², and R³ can be independently selected to be linear,cyclic, branched or substituted alkyl, hydrogen or aryl groups; andremoving excess second reactant and reaction byproducts, if any, fromthe reaction chamber.

Methods for depositing nanolaminate thin films by an atomic layerdeposition (ALD) process are provided herein. The methods comprise afirst deposition cycle comprising alternate and sequential pulses of afirst precursor and a second precursor, the second precursor comprisingA(SiR¹R²R³)_(x), wherein R¹, R², and R³ are alkyl groups with one ormore carbon atoms and A is Sb, Te, or Se, wherein x is 3 when A is Sband x is 2 when A is Te or Se; and a second deposition cycle comprisingalternate and sequential pulses of a third precursor and a fourthprecursor, the fourth precursor comprising A(SiR¹R²R³)_(x), wherein R¹,R², and R³ are alkyl groups with one or more carbon atoms and A is Sb,Te, or Se, and wherein x is 3 when A is Sb and x is 2 when A is Te orSe.

ALD methods are also disclosed herein for depositing thin filmscomprising: Sb—Te, Ge—Te, Ge—Sb, Ge—Sb—Te, Al—Sb, In—Sb, Ga—Sb, Zn—Sb,Co—Sb, Ga—As, As—Te, As—Se, In—As, In—Ga—As, As—S, Al—As, Bi, Bi—Te,Bi—Se, In—Bi, Sb—Bi, Ga—Bi, Al—Bi, P—Te, P—Se, In—P, Ga—P, Cu—P, Al—P,B—N, Al—N, Ga—N, In—N and combinations thereof, along with relatedcompositions and structures.

In some embodiments, nanolaminate films can be formed comprising thematerials disclosed herein. In some embodiments, nanolaminates areformed using multiple ALD cycles to deposit a first film followed bymultiple ALD cycles to form a second film having a composition differentfrom the first film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a flow chart generally illustrating a method for forming a Sbfilm in accordance with one embodiment.

FIG. 2 a flow chart generally illustrating a method for forming a Ge—Sbfilm in accordance with one embodiment.

FIG. 3 is a graph of the average growth rate per cycle for Sb thin filmsversus precursor pulse length.

FIG. 4 is a gracing incidence x-ray diffractogram of a Sb thin film;

FIG. 5 is a graph of the composition of a Sb—Te film as measured byenergy dispersive x-ray (EDX) analysis.

FIG. 6 is a graph of the average growth rate per cycle for Sb—Te thinfilms versus the cycling ratio between Sb—Te and Sb cycles.

FIG. 7 is a gracing incidence x-ray diffractogram of Sb—Te thin films ofvarious compositions;

FIG. 8 is a graph of the composition of various Ge—Sb films for variousGe—Sb to Sb cycling ratios as measured by EDX analysis.

FIG. 9 is a graph of the average growth rate per cycle for Ge—Sb thinfilms versus the cycling ratio between Ge—Sb and Sb cycling ratio.

FIG. 10 a flow chart generally illustrating a method for synthesizing acompound having the formula Sb(SiR¹R²R³)₃ in accordance with oneembodiment.

FIG. 11 is a graph of nanolaminate composition as a function of theamount of GeTe and Sb₂Te₃ subcycles.

FIG. 12 is a graph of resistivity of GeTe, Sb₂Te₃, GST and thenanolaminates as a function of annealing temperature.

FIGS. 13A and 13B are a HTXRD measurement from room temperature to 405°C. of samples D (13A) and C (13B).

FIG. 14 is a graph of the average growth rate per cycle for Sb thinfilms versus deposition temperature.

FIG. 15 is a time-of-flight elastic recoil detection analysis (TOF-ERDA)of a Sb film deposited at 100° C. by ALD.

FIG. 16(a) illustrates a Sb film deposited on a high aspect ratio trenchstructure and FIGS. 16(b)-(d) are Sb nanotubes.

FIG. 17 is a graph illustrating various compositions of Ge—Te—Sb thinfilms formed by various ALD processes.

FIG. 18 is a graph of the average growth rate per cycle for Ga—Sb thinfilms versus GaCl₃ precursor pulse length.

FIG. 19 is a graph of the average growth rate per cycle for Ga—Sb thinfilms versus (Et₃Si)₃Sb precursor pulse length.

FIG. 20 is a graph of the composition of a Al—Sb film as measured by EDXanalysis.

FIG. 21 is a TOF-ERDA depth profile of a Ge₂₂Sb₇₈ thin film deposited byALD.

FIG. 22 is a thermal gravimetric analysis (TGA) graph of Sb(SiMe₃)₃,Sb(SiEt₃)₃, As(SiEt₃)₃ and Bi(SiEt₃)₃, which have been synthesized.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

As discussed above, Sb-containing films find use in a variety ofapplications, including phase change memory (PCM), solar cells, andoptical storage materials. PCM cells can have a variety of differentconfigurations. Typically, the PCM cell includes a transistor and aresistor between a top metal contact and a resistive bottom electrode.Additional PCM configurations are disclosed, for example, in “Phasechange memories: State-of-the-art, challenges and perspectives” byLacaita, Solid-State Electronics 50 (2006) 24-31, which is hereinincorporated by reference in its entirety. Elemental antimony can alsobe used as phase change material. Elemental antimony can also be used asan optical material in super-resolution near-field structures(super-RENS).

Group VA is used herein for clarity although IUPAC nomenclature now usesthe term group 15. As used herein Group VA covers the elements of group15. Group III or IIIA is used herein although IUPAC nomenclature nowuses the term group 13. As used herein Group III or IIIA covers theelements of group 13. The term group III-V semiconductor covers asemiconductor with an element from group 15 and an element group 13.

The terms “film” and “thin film” are also used herein for simplicity.“Film” and “thin film” are meant to mean any continuous ornon-continuous structures deposited by the methods disclosed herein. Forexample, “film” and “thin film” could include nanorods, nanotubes ornanoparticles.

While the embodiments disclosed herein are discussed in the generalcontext of PCM, the skilled artisan will appreciate that the principlesand advantages taught herein will have application to other devices andapplications. Furthermore, while a number of processes are disclosedherein, one of ordinary skill in the art will recognize the utility ofcertain of the disclosed steps in the processes, even in the absence ofsome of the other disclosed steps, and similarly that subsequent, priorand intervening steps can be added.

Antimony-telluride (including Sb₂Te and Sb₂Te₃), Germanium-telluride(including GeTe), germanium-antimony-telluride (GST; Ge₂Sb₂Te₅),bismuth-telluride Bi—Te (including Bi₂Te₃), and zinc-telluride(including ZnTe) thin films can be deposited on a substrate by atomiclayer deposition (ALD) type processes. Methods and precursors fordepositing thin films comprising Te and Se are disclosed in ApplicationNos. 61/048,077, filed on Apr. 25, 2008; 61/112,128, filed Nov. 6, 2008;61/117,896, filed Nov. 25, 2008; and Ser No. 12/429,133 filed Apr. 23,2009, the disclosures of which are hereby incorporated in theirentirety.

More precise control over the composition of the Sb-containing thinfilms is desired. The methods disclosed herein describe ALD cycles fordepositing elemental antimony films. The elemental antimony cycles canbe used with other ALD cycles to deposit a thin film with a preciseantimony composition to achieve a thin film with desired properties.

Antimony has several oxidation states, including −3, +3, 0 and +5, ofwhich +3 is most common. Tellurium has several oxidation states,including −2, 0, +2, +4, and +6. A stoichiometric Sb—Te film with Te ina −2 oxidation state comprises Sb₂Te₃. Germanium (Ge) has oxidationstates of 0, +2, and +4.

Tellurium (Te) compounds, where Te has an oxidation state of −2, aregenerally called tellurides. Tellurium compounds, where Te has anoxidation state of 0, are generally called tellurium compounds. Theseoxidation states in many Te compounds can be just nominal or formalexpressions, in reality the situation might be more complex. However,for the sake of simplicity, as used herein thin films comprising Te arereferred to as tellurides. Thus films referred to as tellurides hereinmay contain Te with oxidations states other than −2, for example,oxidation states of 0, +2, +4, and +6. It will be apparent to theskilled artisan when a particular oxidation state is intended.

ALD type processes are based on controlled, self-limiting surfacereactions of precursor chemicals. Gas phase reactions are avoided byfeeding the precursors alternately and sequentially into the reactionchamber. Vapor phase reactants are separated from each other in thereaction chamber, for example, by removing excess reactants and/orreactant byproducts from the reaction chamber between reactant pulses.

Briefly, a substrate is loaded into a reaction chamber and is heated toa suitable deposition temperature, generally at lowered pressure.Deposition temperatures are maintained below the thermal decompositiontemperature of the reactants but at a high enough level to avoidcondensation of reactants and to provide the activation energy for thedesired surface reactions. Of course, the appropriate temperature windowfor any given ALD reaction will depend upon the surface termination andreactant species involved. Here, the temperature varies depending on thetype of film being deposited and is preferably at or below about 400°C., more preferably at or below about 200° C. and most preferably fromabout 20° C. to about 200° C.

A first reactant is conducted or pulsed into the chamber in the form ofa vapor phase pulse and contacted with the surface of the substrate.Conditions are preferably selected such that no more than about onemonolayer of the first reactant is adsorbed on the substrate surface ina self-limiting manner. The appropriate pulsing times can be readilydetermined by the skilled artisan based on the particular circumstances.Excess first reactant and reaction byproducts, if any, are removed fromthe reaction chamber, such as by purging with an inert gas.

Purging the reaction chamber means that vapor phase precursors and/orvapor phase byproducts are removed from the reaction chamber such as byevacuating the chamber with a vacuum pump and/or by replacing the gasinside the reactor with an inert gas such as argon or nitrogen. Typicalpurging times are from about 0.05 to 20 seconds, more preferably betweenabout 1 and 10, and still more preferably between about 1 and 2 seconds.However, other purge times can be utilized if necessary, such as wherehighly conformal step coverage over extremely high aspect ratiostructures or other structures with complex surface morphology isneeded.

A second gaseous reactant is pulsed into the chamber where it reactswith the first reactant bound to the surface. Excess second reactant andgaseous byproducts of the surface reaction, if any, are removed from thereaction chamber, preferably by purging with the aid of an inert gasand/or evacuation. The steps of pulsing and purging are repeated until athin film of the desired thickness has been formed on the substrate,with each cycle leaving no more than a molecular monolayer. Additionalphases comprising provision of a reactant and purging of the reactionspace can be included to form more complicated materials, such asternary materials.

As mentioned above, each pulse or phase of each cycle is preferablyself-limiting. An excess of reactant precursors is supplied in eachphase to saturate the susceptible structure surfaces. Surface saturationensures reactant occupation of all available reactive sites (subject,for example, to physical size or “steric hindrance” restraints) and thusensures excellent step coverage. Typically, less than one molecularlayer of material is deposited with each cycle, however, in someembodiments more than one molecular layer is deposited during the cycle.

Removing excess reactants can include evacuating some of the contents ofthe reaction space and/or purging the reaction space with helium,nitrogen or another inert gas. In some embodiments purging can compriseturning off the flow of the reactive gas while continuing to flow aninert carrier gas to the reaction space.

The precursors employed in the ALD type processes may be solid, liquidor gaseous materials under standard conditions (room temperature andatmospheric pressure), provided that the precursors are in vapor phasebefore they are conducted into the reaction chamber and contacted withthe substrate surface. “Pulsing” a vaporized precursor onto thesubstrate means that the precursor vapor is conducted into the chamberfor a limited period of time. Typically, the pulsing time is from about0.05 to 10 seconds. However, depending on the substrate type and itssurface area, the pulsing time may be even higher than 10 seconds.Pulsing times can be on the order of minutes in some cases. The optimumpulsing time can be determined by the skilled artisan based on theparticular circumstances.

The mass flow rate of the precursors can also be determined by theskilled artisan. In some embodiments the flow rate of metal precursorsis preferably between about 1 and 1000 sccm without limitation, morepreferably between about 100 and 500 sccm.

The pressure in the reaction chamber is typically from about 0.01 toabout 20 mbar, more preferably from about 1 to about 10 mbar. However,in some cases the pressure will be higher or lower than this range, ascan be determined by the skilled artisan given the particularcircumstances.

Before starting the deposition of the film, the substrate is typicallyheated to a suitable growth temperature. The growth temperature variesdepending on the type of thin film formed, physical properties of theprecursors, etc. The growth temperatures are discussed in greater detailbelow in reference to each type of thin film formed. The growthtemperature can be less than the crystallization temperature for thedeposited materials such that an amorphous thin film is formed or it canbe above the crystallization temperature such that a crystalline thinfilm is formed. The preferred deposition temperature may vary dependingon a number of factors such as, and without limitation, the reactantprecursors, the pressure, flow rate, the arrangement of the reactor,crystallization temperature of the deposited thin film, and thecomposition of the substrate including the nature of the material to bedeposited on. The specific growth temperature may be selected by theskilled artisan.

Examples of suitable reactors that may be used include commerciallyavailable ALD equipment such as the F-120® reactor, Pulsar® reactor andAdvance® 400 Series reactor, available from ASM America, Inc of Phoenix,Ariz. and ASM Europe B.V., Almere, Netherlands. In addition to these ALDreactors, many other kinds of reactors capable of ALD growth of thinfilms, including CVD reactors equipped with appropriate equipment andmeans for pulsing the precursors can be employed. In some embodiments aflow type ALD reactor is used. Preferably, reactants are kept separateuntil reaching the reaction chamber, such that shared lines for theprecursors are minimized. However, other arrangements are possible, suchas the use of a pre-reaction chamber as described in U.S. applicationSer. No. 10/929,348, filed Aug. 30, 2004 and Ser. No. 09/836,674, filedApr. 16, 2001, the disclosures of which are incorporated herein byreference.

The growth processes can optionally be carried out in a reactor orreaction space connected to a cluster tool. In a cluster tool, becauseeach reaction space is dedicated to one type of process, the temperatureof the reaction space in each module can be kept constant, whichimproves the throughput compared to a reactor in which is the substrateis heated up to the process temperature before each run.

A stand-alone reactor can be equipped with a load-lock. In that case, itis not necessary to cool down the reaction space between each run.

The examples descried herein illustrate certain preferred embodiments.They were carried out in an F-120™ ALD reactor supplied by ASMMicrochemistry Oy, Espoo.

Sb Precursors for Atomic Layer Deposition

Precursors that may be used in various ALD processes disclosed hereinare discussed below.

In some embodiments Sb precursors that may be used include, Sb halides,such as SbCl₃ and SbI₃, Sb alkoxides, such as Sb(OEt)₃ and Sb amides.

In some embodiments the Sb precursor has Sb bound to three siliconatoms. For example it can have a general formula of Sb(AR¹R²R³)₃,wherein A is Si or Ge, and R¹, R², and R³ are alkyl groups comprisingone or more carbon atoms. Each of the R¹, R² and R³ ligands can beselected independently of each other. The R¹, R², and R³ alkyl groupscan be selected independently of each other in each ligand based on thedesired physical properties of the precursor such as volatility, vaporpressure, toxicity, etc. In some embodiments, R¹, R² and/or R³ can behydrogen, alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R²,R³ can be any organic groups containing heteroatoms, such as N, O, F,Si, P, S, Cl, Br or I. In some embodiments R¹, R², R³ can be halogenatoms. In some embodiments the Sb precursor have a general formula ofSb(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkyl groups comprising one ormore carbon atoms. In some embodiments, R¹, R² and/or R³ can beunsubstituted or substituted C₁-C₂ alkyls, such as methyl or ethylgroups. The R¹, R², and R³ alkyl groups can be selected independently ofeach other in each ligand based on the desired physical properties ofthe precursor such as volatility, vapor pressure, toxicity, etc In someembodiments the Sb precursor is Sb(SiMe₂ ^(t)Bu)₃. In other embodimentsthe precursor is Sb(SiEt₃)₃ or Sb(SiMe₃)₃. In more preferred embodimentsthe precursor has a Sb—Si bond and most preferably a three Si—Sb bondstructure.

In some embodiments the Sb precursor has a general formula ofSb[A¹(X¹R¹R²R³)₃][A²(X²R⁴R⁵R⁶)₃][A³(X³R⁷R⁸R⁹)₃] wherein A¹, A², A³ canbe independently selected to be Si or Ge and wherein R¹, R², R³, R⁴, R⁵,R⁶, R⁷, R⁸, and R⁹, can be independently selected to be alkyl, hydrogen,alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸, and R⁹ can be any organic groups containing alsoheteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. In some embodimentsone or more R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ can be halogen atoms.In some embodiments X¹, X², and X³ can be Si, Ge, N, or O. In someembodiments X¹, X², and X³ are different elements. In embodiments when Xis Si then Si will be bound to three R groups, for exampleSb[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃]. In embodiments when Xis N then nitrogen will only be bound to two R groupsSb[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃]. In embodiments when X is O, theoxygen will only be bound to one R group, for exampleSb[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃]. R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹groups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc.

In some embodiments, the Sb precursor is selected from the groupconsisting of: Sb[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃],Sb[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃],Sb[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃], and Sb[SiR¹R²][SiR³R⁴][SiR⁵R⁶] with adouble bond between silicon and one of the R groups. In otherembodiments the Sb precursor comprises: a ring or cyclical configurationcomprising a Sb atom and multiple Si atoms; or comprises more than oneSb atom. In these embodiments R¹, R², R³, R⁴, R⁵ and R⁶, are selectedfrom the group consisting of alkyl, hydrogen, alkenyl, alkynyl, or arylgroups.

In some embodiments the Sb precursor has a formula similar to theformulas described above, however the Si atom has a double bond to oneof the R groups in the ligand (e.g. Sb—Si═). For example, a partialstructure of the precursor formula is represented below:

In some embodiments the precursor contains multiple atoms of Si and Sb.For example, a partial structure of a precursor in one embodiment isrepresented below:

The Si and Sb atoms in the partial formulas pictured above can also bebound to one or more R groups. In some embodiments, any of the R groupsdescribed herein can be used.

In some embodiments the precursor contains a Si—Sb—Si bond structure ina cyclical or ring structure. For example, a partial structure of aprecursor in one embodiment is represented below.

The R group can comprise an alkyl, alkenyl, alkynyl, alkylsilyl,alkylamine or alkoxide group. In some embodiments the R group issubstituted or branched. In some embodiments the R group is notsubstituted and/or is not branched. The Si and Sb atoms in the partialformula pictured above can also be bound to one or more R groups. Insome embodiments, any of the R groups described herein can be used.

As Precursors for Atomic Layer Deposition

Precursors comprising As that are similar to the precursors comprisingSb. described herein can be used. Formally As have oxidation state −IIIin compounds described herein.

In some embodiments the As precursor has As bound to three siliconatoms. For example it can have a general formula of As(AR¹R²R³)₃,wherein A is Si or Ge, and R¹, R², and R³ are alkyl groups comprisingone or more carbon atoms. The R¹, R², and R³ alkyl groups can beselected independently of each other in each ligand based on the desiredphysical properties of the precursor such as volatility, vapor pressure,toxicity, etc. In some embodiments, R¹, R² and/or R³ can be hydrogen,alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R², R³ can beany organic groups containing heteroatoms, such as N, O, F, Si, P, S,Cl, Br or I. In some embodiments R¹, R², R³ can be halogen atoms. Insome embodiments the As precursor have a general formula ofAs(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkyl groups comprising one ormore carbon atoms. The R¹, R², and R³ alkyl groups can be selectedindependently of each other in each ligand based on the desired physicalproperties of the precursor such as volatility, vapor pressure,toxicity, etc. In more preferred embodiments the precursor has an As—Sibond and most preferably a three Si—As bond structure. In someembodiments the As precursor is As(SiMe₂ ^(t)Bu)₃. In other embodimentsthe precursor is As(SiEt₃)₃ or As(SiMe₃)₃. For example, As(SiMe₃)₃ iscommercially available and can be used in some embodiments.

In some embodiments the As precursor has a general formula ofAs[A¹(X¹R¹R²R³)₃][A²(X²R⁴R⁵R⁶)₃][A³(X³R⁷R⁸R⁹)₃] wherein A¹, A², A³ canbe independently selected to be Si or Ge and wherein R¹, R², R³, R⁴, R⁵,R⁶, R⁷, R⁸, and R⁹, can be independently selected to be alkyl, hydrogen,alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸, and R⁹ can be any organic groups containing alsoheteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. In some embodimentsone or more R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ can be halogen atoms.In some embodiments X¹, X², and X³ can be Si, Ge, N, or O. In someembodiments X¹, X², and X³ are different elements. In embodiments when Xis Si then Si will be bound to three R groups, for exampleAs[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃]. In embodiments when Xis N then nitrogen will only be bound to two R groupsAs[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃]. In embodiments when X is O, theoxygen will only be bound to one R group, for exampleAs[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃]. R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹groups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc.

Bi Precursors for Atomic Layer Deposition

Precursors comprising Bi that are similar to the precursors comprisingSb. described herein can be used. Formally oxidation state of Bi can beeither −III or +III in compounds described herein as theelectronegativity of Bi is close to Si electronegativity. It must beemphasized that the oxidation state values are just formal, like in Ascase.

In some embodiments the Bi precursor has Bi bound to three siliconatoms. For example it can have a general formula of Bi(AR¹R²R³)₃,wherein A is Si or Ge, and R¹, R², and R³ are alkyl groups comprisingone or more carbon atoms. The R¹, R², and R³ alkyl groups can beselected independently of each other in each ligand based on the desiredphysical properties of the precursor such as volatility, vapor pressure,toxicity, etc. In some embodiments, R¹, R² and/or R³ can be hydrogen,alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R², R³ can beany organic groups containing heteroatoms, such as N, O, F, Si, P, S,Cl, Br or I. In some embodiments R¹, R², R³ can be halogen atoms. Insome embodiments the Bi precursor have a general formula ofBi(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkyl groups comprising one ormore carbon atoms. The R¹, R², and R³ alkyl groups can be selectedindependently of each other in each ligand based on the desired physicalproperties of the precursor such as volatility, vapor pressure,toxicity, etc. In more preferred embodiments the precursor has a Bi—Sibond and most preferably a three Si—Bi bond structure. In someembodiments the Bi precursor is Bi(SiMe₂ ^(t)Bu)₃. In other embodimentsthe precursor is Bi(SiEt₃)₃ or Bi(SiMe₃)₃.

In some embodiments the Bi precursor has a general formula ofBi[A¹(X¹R¹R²R³)₃][A²(X²R⁴R⁵R⁶)₃][A³(X³R⁷R⁸R⁹)₃] wherein A¹, A², A³ canbe independently selected to be Si or Ge and wherein R¹, R², R³, R⁴, R⁵,R⁶, R⁷, R⁸, and R⁹, can be independently selected to be alkyl, hydrogen,alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸ and R⁹ can be any organic groups containing alsoheteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. In some embodimentsone or more R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ can be halogen atoms.In some embodiments X¹, X², and X³ can be Si, Ge, N, or O. In someembodiments X¹, X², and X³ are different elements. In embodiments when Xis Si then Si will be bound to three R groups, for exampleBi[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃]. In embodiments when Xis N then nitrogen will only be bound to two R groupsBi[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃]. In embodiments when X is O, theoxygen will only be bound to one R group, for exampleBi[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃]. R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹groups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc.

P Precursors for Atomic Layer Deposition

Precursors comprising P that are similar to the precursors comprising Sbdescribed herein can be used. Formally P have oxidation state −III incompounds described herein.

In some embodiments the P precursor has P bound to three silicon atoms.For example it can have a general formula of P(AR¹R²R³)₃, wherein A isSi or Ge, and R¹, R², and R³ are alkyl groups comprising one or morecarbon atoms. The R¹, R², and R³ alkyl groups can be selectedindependently of each other in each ligand based on the desired physicalproperties of the precursor such as volatility, vapor pressure,toxicity, etc. In some embodiments, R¹, R² and/or R³ can be hydrogen,alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R², R³ can beany organic groups containing heteroatoms, such as N, O, F, Si, P, S,Cl, Br or I. In some embodiments R¹, R², R³ can be halogen atoms. Insome embodiments the P precursor have a general formula of P(SiR¹R²R³)₃,wherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected independently ofeach other in each ligand based on the desired physical properties ofthe precursor such as volatility, vapor pressure, toxicity, etc. In morepreferred embodiments the precursor has a P—Si bond and most preferablya three Si—P bond structure. In some embodiments the P precursor isP(SiMe₂ ^(t)Bu)₃. In other embodiments the precursor is P(SiEt₃)₃ orP(SiMe₃)₃. For example, P(SiMe₃)₃ is commercially available and can beused in some embodiments.

In some embodiments the P precursor has a general formula ofP[A¹(X¹R¹R²R³)₃][A²(X²R⁴R⁵R⁶)₃][A³(X³R⁷R⁸R⁹)₃] wherein A¹, A², A³ can beindependently selected to be Si or Ge and wherein R¹, R², R³, R⁴, R⁵,R⁶, R⁷, R⁸, and R⁹, can be independently selected to be alkyl, hydrogen,alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸, and R⁹ can be any organic groups containing alsoheteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. In some embodimentsone or more R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, can and R⁹ can be halogenatoms. In some embodiments X¹, X², and X³ can be Si, Ge, N, or O. Insome embodiments X¹, X², and X³ are different elements. In embodimentswhen X is Si then Si will be bound to three R groups, for exampleP[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃]. In embodiments when X isN then nitrogen will only be bound to two R groupsP[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃]. In embodiments when X is O, theoxygen will only be bound to one R group, for exampleP[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃]. R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹groups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc.

N Precursors for Atomic Layer Deposition

Precursors comprising N that are similar to the precursors comprising Sbdescribed herein can be used in some embodiments.

In some embodiments a N precursor has N bound to three silicon atoms.For example it can have a general formula of N(AR¹R²R³)_(x)R_(3−x),wherein x is from 1 to 3, A is Si, Ge or Sn and R, R¹, R², and R³ arealkyl groups comprising one or more carbon atoms. The R¹, R², and R³alkyl groups can be selected independently of each other in each ligandbased on the desired physical properties of the precursor such asvolatility, vapor pressure, toxicity, etc. In some embodiments, R, R¹,R² and/or R³ can be hydrogen, alkenyl, alkynyl or aryl groups. In someembodiments, R, R¹, R², R³ can be any organic groups containingheteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. In some embodimentsR, R¹, R², R³ can be halogen atoms. In some embodiments R, R¹, R², R³are not hydrogen. In some embodiments x is 2 and R is hydrogen.

In some embodiments a N precursor has a general formula ofN(SiR¹R²R³)_(x)R_(3−x), wherein x is from 1 to 3, R¹, R², and R³ arealkyl groups comprising one or more carbon atoms and R is hydrogen. TheR, R¹, R², and R³ alkyl groups can be selected independently of eachother in each ligand based on the desired physical properties of theprecursor such as volatility, vapor pressure, toxicity, etc. In morepreferred embodiments the precursor has a N—Si bond and most preferablya three Si—N bond structure. In some embodiments the N precursor isN(SiMe₂ ^(t)Bu)₃. In other embodiments the precursor is N(SiEt₃)₃ orN(SiMe₃)₃.

In some embodiments the N precursor has a general formula ofN[A¹(X¹R¹R²R³)₃][A²(X²R⁴R⁵R⁶)₃][A³(X³R⁷R⁸R⁹)₃] wherein A¹, A², A³ can beindependently selected to be Si, Ge or Sn and wherein R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸, and R⁹ can be independently selected to be alkyl,hydrogen, alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R²,R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ can be any organic groups containing alsoheteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. In some embodimentsR¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ are not hydrogen. In someembodiments one or more R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ can behalogen atoms. In some embodiments X¹ and X² can be Si, Ge, N, or O. Insome embodiments X¹ and X² are different elements. In embodiments when Xis Si then Si will be bound to three R groups, for exampleN[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃]. In embodiments when X isN then nitrogen will only be bound to two R groupsN[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃]. In embodiments when X is O, theoxygen will only be bound to one R group, for exampleN[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃]. R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹groups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc.

In some embodiments the N precursor has a general formula ofN[A¹(X¹R¹R²R³)₃][A²(X²R⁴R⁵R⁶)₃]H wherein A¹, A² can be independentlyselected to be Si, Ge or Sn and wherein R¹, R², R³, R⁴, R⁵ and R⁶ can beindependently selected to be alkyl, hydrogen, alkenyl, alkynyl or arylgroups. In some embodiments R¹, R², R³, R⁴, R⁵ and R⁶ are not hydrogen.In some embodiments, R¹, R², R³, R⁴, R⁵ and R⁶ can be any organic groupscontaining also heteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. Insome embodiments one or more R¹, R², R³, R⁴, R⁵ and R⁶ can be halogenatoms. In some embodiments X¹ and X² can be Si, Ge, N, or O. In someembodiments X¹ and X² are different elements. In embodiments when X isSi then Si will be bound to three R groups, for exampleN[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃]H. In embodiments when X is N thennitrogen will only be bound to two R groups N[Si(NR¹R²)₃][Si(NR³R⁴)₃]H.In embodiments when X is O, the oxygen will only be bound to one Rgroup, for example N[Si(OR¹)₃][Si(OR²)₃]H. R¹, R², R³, R⁴, R⁵ and R⁶groups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc.

General Description of Group VA Element Containing Precursors for AtomicLayer Deposition

In some embodiments a Group VA element containing precursor has Group VAelement bound to three silicon atoms. For example it can have a generalformula of L(AR¹R²R³)₃, wherein L is Sb, As, Bi or P, wherein A is Si,Sn, or Ge, and R¹, R², and R³ are alkyl groups comprising one or morecarbon atoms. In some embodiments A can be Sn. Each of theAR¹R²R³-ligands can be independently selected of each other. The R¹, R²,and R³ alkyl groups can also be selected independently of each other ineach ligand based on the desired physical properties of the precursorsuch as volatility, vapor pressure, toxicity, etc. In some embodiments,R¹, R² and/or R³ can be hydrogen, alkenyl, alkynyl or aryl groups. Insome embodiments, R¹, R² and/or R³ can be unsubstituted or substitutedC₁-C₂ alkyls, such as methyl or ethyl groups. In some embodiments, R¹,R², R³ can be any organic groups containing heteroatoms, such as N, O,F, Si, P, S, Cl, Br or I. In some embodiments R¹, R², R³ can be halogenatoms. In some embodiments the Group VA element containing precursorhave a general formula of L(SiR¹R²R³)₃, wherein L is Sb, As, Bi or P andwherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected independently ofeach other in each ligand based on the desired physical properties ofthe precursor such as volatility, vapor pressure, toxicity, etc. In someembodiments the VA precursor has a formula of L(SiMe₂ ^(t)Bu)₃. In otherembodiments the precursor is L(SiEt₃)₃ or L(SiMe₃)₃.

In some embodiments the Group VA element containing precursor comprisesa Group VA element bound to one or more of Si, Ge, and Sn. In someembodiments the Group VA element containing precursor has a Group VAelement bound to one, two or three atoms selected from Si, Ge, and Sn.In some embodiments the Group VA element containing precursor comprisesa Group VA element bound to two or three atoms selected from Si, Ge, andSn, wherein there are at least two different atoms selected from Si, Ge,and Sn. In some embodiments the Group VA element containing precursorcomprises a Group VA element bound to one or more Si atoms. For example,it can have a general formula of L(AR¹R²R³)_(x)R_(3−x), wherein x isfrom 1 to 3, L is Sb, As, Bi or P, wherein A is Si, Sn, or Ge, and R,R¹, R², and R³ are alkyl groups comprising one or more carbon atoms. Insome embodiments, R¹, R² and/or R³ can be unsubstituted or substitutedC₁-C₂ alkyls, such as methyl or ethyl groups In some embodiments A canbe Sn. The R, R¹, R², and R³ alkyl groups can be selected independentlyof each other in each ligand based on the desired physical properties ofthe precursor such as volatility, vapor pressure, toxicity, etc. Each ofthe AR¹R²R³-ligands can also be independently selected of each other. Insome embodiments, R, R¹, R² and/or R³ can be hydrogen, alkenyl, alkynylor aryl groups. In some embodiments, R, R¹, R², R³ can be any organicgroups containing heteroatoms, such as N, O, F, Si, P, S, Cl, Br or I.In some embodiments R, R¹, R², R³ can be halogen atoms. In someembodiments R can be amino group. In some embodiments at least one ofthe ligands R, R¹, R², and R³ is selected from linear, branched orcyclic C₁-C₅ alkyls, such as methyl, ethyl, propyl, isopropyl, butyl,isobutyl, tertbutyl, pentyl, isopentyl, tertpentyl.

In some embodiments the Group VA element containing precursor has ageneral formula of L(SiR¹R²R³)_(x)R_(3−x), wherein L is Sb, As, Bi or Pand wherein R, R¹, R², and R³ are alkyl groups comprising one or morecarbon atoms. In some embodiments, R¹, R² and/or R³ can be unsubstitutedor substituted C₁-C₂ alkyls, such as methyl or ethyl groups. The R, R¹,R², and R³ alkyl groups can be selected independently of each other ineach ligand based on the desired physical properties of the precursorsuch as volatility, vapor pressure, toxicity, etc. In some embodimentsthe VA precursor has a formula of L(SiMe₂ ^(t)Bu)₃. In other embodimentsthe precursor is L(SiEt₃)₃ or L(SiMe₃)₃. In some embodiments at leastone of the ligands R, R¹, R², and R³ is selected from linear, branchedor cyclic C₁-C₅ alkyls, such as methyl, ethyl, propyl, isopropyl, butyl,isobutyl, tertbutyl, pentyl, isopentyl, tertpentyl. In some embodimentsR is a linear, branched, unsubstituted or substituted alkyl, alkenyl,alkynyl, alkylsilyl, alkylamine or alkoxide group.

In some embodiments the Group VA element containing precursor comprisesa Group VA element bound to one or more atoms selected from Si, Ge, Snwith a double bond similar to the Sb precursors described herein.

In some embodiments the Group VA element containing precursor has aformula similar to the formulas described above, however the Si or Geatom, which are represented as A in the formulas below, has a doublebond to one of the R groups in the ligand (e.g. A-Si═). For example, apartial structure of the precursor formula is represented below:

In some embodiments the precursor contains multiple Si or Ge atoms. Forexample, a partial structure of a precursor in one embodiment isrepresented below:

The Si or Ge and Group VA element atoms in the partial formulas picturedabove can also be bound to one or more R groups. In some embodiments,any of the R groups described herein can be used.

In some embodiments the precursor contains A-L-A, wherein A is Si or Geand wherein L is Group VA element atom, bond structure in a cyclical orring structure. For example, a partial structure of a precursor in oneembodiment is represented below.

The R group can comprise an alkyl, alkenyl, alkynyl, alkylsilyl,alkylamine or alkoxide group. In some embodiments the R group issubstituted or branched. In some embodiments the R group is notsubstituted and/or is not branched. The A and L atoms in the partialformula pictured above can also be bound to one or more R groups. Insome embodiments, any of the R groups described herein can be used.

In some embodiments the Group VA element containing precursor has ageneral formula of L[A¹(X¹R¹R²R³)₃][A²(X²R⁴R⁵R⁶)₃][A³(X³R⁷R⁸R⁹)₃]wherein L is Sb, As, Bi or P and wherein A¹, A², A³ can be independentlyselected to be Si, Sn, or Ge and wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸and R⁹, can be independently selected to be alkyl, hydrogen, alkenyl,alkynyl or aryl groups. In some embodiments, A¹, A² and/or A³ can beindependently selected to be Sn. In some embodiments, R¹, R², R³, R⁴,R⁵, R⁶, R⁷, R⁸, and R⁹ can be any organic groups containing alsoheteroatoms, such as N, O, F, Si, P, S, Cl, Br or I. In some embodimentsone or more R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ can be halogen atoms.In some embodiments X¹, X², and X³ can be Si, Ge, N, or O. In someembodiments X¹, X², and X³ are different elements. In embodiments when Xis Si then Si will be bound to three R groups, for exampleL[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃]. In embodiments when X isN then nitrogen will only be bound to two R groupsL[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃]. In embodiments when X is O, theoxygen will only be bound to one R group, for exampleL[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃]. L is Sb, As, Bi or P and R¹, R², R³,R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ groups can be selected independently of eachother in each ligand based on the desired physical properties of theprecursor such as volatility, vapor pressure, toxicity, etc.

In some embodiments, the Group VA element containing precursor isselected from the group consisting of:L[Si(SiR¹R²R³)₃][Si(SiR⁴R⁵R⁶)₃][Si(SiR⁷R⁸R⁹)₃],L[Si(NR¹R²)₃][Si(NR³R⁴)₃][Si(NR⁵R⁶)₃], L[Si(OR¹)₃][Si(OR²)₃][Si(OR³)₃],and L[SiR¹R²][SiR³R⁴][SiR⁵R⁶] with a double bond between silicon and oneof the R groups. In other embodiments the Sb precursor comprises: a ringor cyclical configuration comprising a Sb atom and multiple Si atoms; orcomprises more than one Sb atom. In these embodiments L is Sb, As, Bi orP and R¹, R², R³, R⁴, R⁵ and R⁶, are selected from the group consistingof alkyl, hydrogen, alkenyl, alkynyl, or aryl groups.

In some embodiments the Group VA element containing precursor has aformula similar to the formulas described above, however the Si atom hasa double bond to one of the R groups in the ligand (e.g. L-Si═). L isselected from the group of consisting Sb, As, Bi or P. For example, apartial structure of the precursor formula is represented below:

In some embodiments the precursor contains multiple atoms of Si and L. Lis selected from the group of consisting Sb, As, Bi or P. For example, apartial structure of a precursor in one embodiment is represented below:

The Si and L atoms in the partial formulas pictured above can also bebound to one or more R groups. In some embodiments, any of the R groupsdescribed herein can be used.

In some embodiments the precursor contains a Si-L-Si bond structure in acyclical or ring structure. L is selected from the group of consistingSb, As, Bi or P. For example, a partial structure of a precursor in oneembodiment is represented below.

The R group can comprise an alkyl, alkenyl, alkynyl, alkylsilyl,alkylamine or alkoxide group. In some embodiments the R group issubstituted or branched. In some embodiments the R group is notsubstituted and/or is not branched. The Si and L atoms in the partialformula pictured above can also be bound to one or more R groups. L isselected from the group of consisting Sb, As, Bi or P. In someembodiments, any of the R groups described herein can be used.

In some embodiments, an additional precursor to be used in combinationwith the Group VA element containing precursors described herein, is notan oxygen source. The term “oxygen source” comprises oxygen precursors,such as water, ozone, alcohol, oxygen atoms, oxygen plasma and oxygenradicals, typically used in ALD for depositing metal oxides. Inpreferred embodiments the other precursor is not water, ozone, oralcohol. In some embodiments plasma is not used.

In other embodiments, the other precursor to be used in combination withthe Group VA element-containing precursors described herein can alsocontain the same Group VA element as the Group VA-element containingprecursor, such that the deposited film is an elemental film comprisingthe Group VA element. The other precursor may be, for example, a halideof a Group VA element, such as chloride, fluoride, bromide or iodide. Insome embodiments the other precursor is SbCl₃ or BiCl₃ and the filmsdeposited are elemental Sb or elemental Bi films, respectively.

Atomic Layer Deposition of Group Va Element Containing Thin Films

In some embodiments any of the precursors disclosed herein can be usedto deposit a thin film comprising a Group VA element.

In some embodiments elemental Group VA elements are deposited. In someembodiments elemental Sb, As, Bi, or P is deposited.

In some embodiments the deposited film comprising a Group VA elementcomprises one or more additional elements. In some embodiments a metal,non-metal, or metalloid can also be included in the deposited thin filmscomprising a Group VA element.

In some embodiments the substrate temperature when depositing the thinfilm comprising a Group VA element is from about 20° C. to about 500° C.In some embodiments the temperature is from about 50° C. to about 400°C. In some embodiments the temperature is from about 50° C. to about300° C.

The growth rate per cycle when depositing thin films comprising a GroupVA element can vary based on the precursors used and the reactor processconditions. The growth rate per cycle as used herein refers to theaverage growth rate per cycle with the cycle including the provision ofone pulse of two different reactants. In some embodiments the averagegrowth rate per cycle is from about 0.05 Å/cycle to about 2.5 Å/cycle.In some embodiments the average growth rate per cycle is from about 0.1Å/cycle to about 1.5 Å/cycle. In some embodiments the average growthrate per cycle is from about 0.2 Å/cycle to about 1.0 Å/cycle.

In some embodiments Group VA element containing thin films are dopedwith one or more dopants selected but not limited to those from thegroup consisting of O, N, C, Si, Sn, Ag, Al, Ga, P, Fe, Ge, In, Ag, Se,Te or Bi.

Atomic Layer Deposition of N Containing Thin Films

In some embodiments N precursors disclosed herein can be used to deposita thin film comprising N. In some embodiments the thin film does notcomprise a transition metal. In some embodiments one or more elements inthe thin films are selected from the group consisting of elements fromGroups IIIA to VIA i.e. Groups 13 to 16 according to the IUPAC. In someembodiments one or more elements in the thin films are selected from thegroup consisting of N, B, Al, Ga and In. In some embodiments the thinfilms are selected from the group consisting of BN, AlN, GaN and InN. Insome embodiments the thin film comprising N is deposited that is not SiNor does not contain Si or Ge.

In some embodiments the deposited film comprising N comprises one ormore additional elements. In some embodiments the deposited filmcomprising N is used for doping a phase change material, such asGe—Sb—Te, with nitrogen. In some embodiments the precursor comprising Ncan be used in deposition cycles in combination with the Ge, Sb, and Tedeposition cycles disclosed herein to deposit a thin film comprisingGe—Sb—Te doped with nitrogen.

In some embodiments the substrate temperature when depositing the thinfilm comprising N is from about 20° C. to about 500° C. In someembodiments the temperature is from about 50° C. to about 400° C. Insome embodiments the temperature is from about 50° C. to about 300° C.

The growth rate per cycle when depositing thin films comprising N canvary based on the precursors used and the reactor process conditions.The growth rate per cycle as used herein refers to the average growthrate per cycle with the cycle including the provision of one pulse oftwo different reactants. In some embodiments the average growth rate percycle is from about 0.05 Å/cycle to about 2.5 Å/cycle. In someembodiments the average growth rate per cycle is from about 0.1 Å/cycleto about 1.5 Å/cycle. In some embodiments the average growth rate percycle is from about 0.2 Å/cycle to about 1.0 Å/cycle.

In some embodiments the N containing thin films are doped with one ormore dopants selected but not limited to those from the group consistingof O, N, C, Si, Sn, Ag, Al, Ga, P, Fe, Ge, In, Ag, Se, Te or Bi.

Group VA Precursors Comprising Sn

In some embodiments the Group VA element containing precursor comprisesa Group VA element bound to three tin (Sn) atoms. For example the GroupVA element containing precursor can have a general formula ofL(SnR¹R²R³)₃, wherein L is Sb, As, Bi or P, and R¹, R², and R³ are alkylgroups comprising one or more carbon atoms. The R¹, R², and R³ alkylgroups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc. In some embodiments, R¹, R² and/or R³ canbe hydrogen, alkenyl, alkynyl or aryl groups. In some embodiments, R¹,R², R³ can be any organic groups containing heteroatoms, such as N, O,F, Si, P, S, Cl, Br or I. In some embodiments R¹, R², R³ can be halogenatoms. In some embodiments the Group VA element containing precursorhave a general formula of L(SnR¹R²R³)₃, wherein L is Sb, As, Bi or P andwherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected independently ofeach other in each ligand based on the desired physical properties ofthe precursor such as volatility, vapor pressure, toxicity, etc. In someembodiments the VA precursor has a formula of L(SnMe₂ ^(t)Bu)₃. In otherembodiments the precursor is L(SnEt₃)₃ or L(SnMe₃)₃.

Atomic Layer Deposition of Sb

In some embodiments, elemental antimony (Sb) films are deposited by ALDpreferably without the use of plasma.

ALD deposition cycles that deposit elemental antimony are useful in avariety of applications. For example, antimony can be used in manyapplications including optical storage materials, semiconductor mixtures(compound, ternary, and quaternary mixtures) and non-volatile phasechange memories.

The discovery of suitable Sb precursors for use in an ALD processwithout plasma allows for deposition of elemental antimony. In someembodiments, elemental antimony can be used as a phase change material.In some embodiments, Sb deposition cycles can also be used incombination with deposition cycles of other materials. The ratio ofcycles can be selected to control the stoichiometry, including Sbcontent, in the deposited film to achieve a film with a desiredcomposition and structure. For example, phase change memory filmscomprising Sb—Te, Ge—Sb—Te, and Ge—Sb can be deposited.

FIG. 1 is a flow chart generally illustrating a method for forming a Sbthin film 10 in accordance with one embodiment. According to someembodiments, an elemental Sb thin film is formed on a substrate in areaction chamber by an ALD type process comprising multiple Sbdeposition cycles, each deposition cycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a first        Sb precursor 11 into the reaction chamber to form no more than        about a single molecular layer of the Sb precursor on the        substrate;    -   removing excess first reactant from the reaction chamber 13;    -   providing a second vapor phase reactant pulse comprising a        second Sb precursor 15 to the reaction chamber such that the        second Sb precursor reacts with the first Sb precursor on the        substrate to form Sb; and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber 17.

This can be referred to as the Sb deposition cycle. Each Sb depositioncycle typically forms at most about one monolayer of Sb. The Sbdeposition cycle is repeated until a film of a desired thickness isformed 19. In some embodiments a Sb film of from about 10 Å to about2000 Å, preferably from about 50 Å to about 500 Å is formed.

Although the illustrated Sb deposition cycle begins with provision ofthe first Sb precursor, in other embodiments the deposition cycle beginswith the provision of the second Sb precursor. It will be understood bythe skilled artisan that provision of the first Sb precursor and secondSb precursor are interchangeable in the ALD cycle.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of Sb precursorwhile continuing the flow of an inert carrier gas such as nitrogen orargon.

In preferred embodiments the first Sb precursor has a formula of SbX₃,wherein X is a halogen element. More preferably the Sb source is SbCl₃,SbBr₃ or SbI₃.

In some embodiments, the other reactant to be used in combination withthe Sb(SiR¹R²R³)₃ precursors described herein, is not an oxygen source.The term “oxygen source” refers to reactants that comprise oxygen, suchas water, ozone, alcohol, oxygen atoms, oxygen plasma and oxygenradicals, typically used in ALD for depositing metal oxides. Inpreferred embodiments the other precursor is not water, ozone oralcohol.

In some embodiments the other reactant to be used in combination withthe Sb(SiR¹R²R³)₃ precursors disclosed herein is not an aminogermaniumprecursor, such as tetraminogermanium or organotellurium precursor. Insome embodiments the other reactant to be used in combination with theSb(SiR¹R²R³)₃ precursors disclosed herein is not a chalcogenideprecursor. In some embodiments the other reactant to be used incombination with the Sb(SiR¹R²R³)₃ precursors disclosed herein does notcontain plasma or an excited species. In some embodiments the otherreactant to be used in combination with the Sb(SiR¹R²R³)₃ precursorsdisclosed herein does not contain nitrogen. In some embodiments theother reactant to be used in combination with the Sb(SiR¹R²R³)₃precursors disclosed herein is not an alkoxide substituted precursor. Insome embodiments the other reactant to be used in combination with theSb(SiR¹R²R³)₃ precursors disclosed herein is not an amino substitutedprecursor. In some embodiments the other reactant to be used incombination with the Sb(SiR¹R²R³)₃ precursors disclosed herein is not analkyl substituted precursor. In some embodiments the other reactant tobe used in combination with the Sb(SiR¹R²R³)₃ precursors disclosedherein does not contain a direct Sb—C bond.

The Sb, As, Bi, N and P center atoms of the Sb, As, Bi, N and Pprecursors disclosed herein can be bonded to Si, Ge, or Sn atoms. Sb,As, Bi, N and P are more electronegative than Si, Ge or Sn, which willcreate polarity in bonds and thus a partial negative charge on the Sb,As, Bi, N and P center atoms of the Sb, As, Bi, N and P precursorsdisclosed herein. In some embodiments, the Sb, As, Bi, N and P centeratoms can have a negative oxidation state. It is believed, although notbeing bound to any theory, that the slight partial negative charge ofthe center atom in the precursors disclosed herein, for example theslight partial negative charge of As in As(SiEt₃)₃ or Sb in Sb(SiEt₃)₃,combined with the partial positive charge of the center atom in theother precursor, for example the partial positive charge of Ga in GaCl₃or Sb in SbCl₃, makes the precursor combination successful and filmdeposition, for example Ga—As or Sb film deposition, possible.

In some embodiments the other reactant to be used in combination withthe Sb(SiR¹R²R³)₃ precursors disclosed herein is not a reducing agent,such as hydrogen, H₂/plasma, amine, imine, hydrazine, silane, silylchalcogenide, germane, ammonia, alkane, alkene or alkyne. As used hereina reducing agent refers to a compound capable of reducing an atom of theother reactant, usually the atom which will be deposited in the film inan ALD process and sometimes to elemental form. At the same time thereducing agent can be oxidized. It may be noted that with oxidativechemistry, for example with an oxidation agent, it is also possible toproduce elemental films if the formal oxidation states of the atom,which will be deposited, are negative in the other precursor. In someembodiments the Sb(SiR¹R²R³)₃ precursors disclosed herein acts as areducing agent in an ALD process.

In some embodiments the other reactant to be used in combination withSb(SiR¹R²R³)₃ precursors disclosed herein is an oxidizing precursor,such as SbCl₃. Preferably the oxidizing precursor is not water, alcoholor ozone. As used herein an oxidizing precursor is a precursor, whichhas a partial positive charge in the center atom of the molecule, suchas Sb in case of SbCl₃ or Ga in case of GaCl₃, and thus center atoms canbe considered to have positive oxidation states. The partial positivecharge of the oxidizing precursors will be decreased in the depositedfilm i.e. the center atom of the molecule can be considered to besomewhat reduced although no real oxidation state increase has happened.In some embodiments the antimony deposition cycle only uses two reactivecompounds.

Preferably, the second reactant is a Sb precursor with a formula ofSb(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkyl groups comprising one ormore carbon atoms. The R¹, R², and R³ alkyl groups can be selected basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc

In some embodiments the first Sb precursor is SbCl₃ and the second Sbprecursor is Sb(SiEt₃)₃.

The substrate temperature during forming the Sb thin film deposition ispreferably less than 250° C. and more preferably less than 200° C. andeven more preferably below 150° C.

Pressure of the reactor can vary much depending from the reactor usedfor the depositions. Typically reactor pressures are below normalambient pressure.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors. Theevaporation temperatures for the second Sb precursor, such asSb(SiEt₃)₃, which can be synthesized by the methods described herein, istypically about 85° C. The evaporation temperature for the first Sbprecursor, such as SbCl₃, is typically about 30° C. to 35° C.

The skilled artisan can determine the optimal reactant pulse timesthrough routine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited Sb thin film.Preferably the first and second Sb reactants are pulsed for about 0.05to 10 seconds, more preferably about 0.2 to 4 seconds, and mostpreferably about 1 to 2 seconds. The purge steps in which excessreactant and reaction by-products, if any, are removed are preferablyabout 0.05 to 10 seconds, more preferably about 0.2-4 seconds, and mostpreferably 1 to 2 seconds in length.

The growth rate of the elemental Sb thin films will vary depending onthe reaction conditions. As described below, in initial experiments, thegrowth rate varied between about 0.3 and about 0.5 Å/cycle.

In some embodiments, a Sb thin film is deposited on a substrate andforms the active material in a PCM cell. In some embodiments, the Sbthin film is deposited on a substrate and used in a super-RENS device.The Sb thin film preferably has a thickness of about 10 Å to about 2000Å.

In some embodiments, one or more dopants selected from the groupconsisting of O, N, C, Si, Sn, Ag, Al, Ga, P, Fe, Ge, In, Ag, Se, Te orBi, but not limited to those, is introduced into film. The precursorcomprising dopant reacts preferably, but not necessarily, with the Sbprecursors described herein.

EXAMPLE 1

Elemental Sb thin films were formed using alternating and sequentialpulses of SbCl₃ and Sb(SiEt₃)₃. 1000 cycles were applied. The elementalSb thin films were formed on soda lime glass and silicon substrates withnative oxide. Sb(SiEt₃)₃ is a liquid at room temperature and wasevaporated from an open boat at a temperature of 85° C. The substratetemperature during deposition was 95° C. The pulse and purge length forthe SbCl₃ precursor was 1 second and 2 seconds, respectively. The pulselength for Sb(SiEt₃)₃ was varied between 0.5 and 2.0 seconds, with apurge length of 2 seconds. FIG. 3 shows the average growth rate percycle for Sb films deposited at 0.5, 1.0, and 2.0 second pulse lengthsof (Et₃Si)₃Sb. FIG. 3 shows a maximum growth rate of around 0.45Å/cycle. The antimony films were clear and mirror like as deposited.

FIG. 4 shows a gracing incidence XRD (GIXRD) pattern of the Sb filmdeposited as described in reference to FIG. 3 using a 1 second(Et₃Si)₃Sb pulse length.

The GIXRD pattern shows a polycrystalline Sb film with all of thereflections identified as rhombohedral Sb (iron black, PDF 00-035-0732).The deposited film was also studied by energy dispersive x-ray (EDX)measurement. The EDX measurement confirmed that the films consisted ofantimony with no chlorine present in the deposited film. Film thicknesswere about 45 nm.

COMPARATIVE EXAMPLE 1

Deposition experiments using (Et₃Si)₃Sb+CH₃OH were conducted at 100, 200and 300° C. Pulse/purge times for (Et₃Si)₃Sb and CH₃OH were 2.0/2.0 sand 1.0/2.0 s, respectively. No film was deposited on soda lime ornative oxide SiO₂/Si substrates when 1000 cycles was applied in theF-120™ reactor. The process was also studied using an in situ ALDreactor equipped with a quartz crystal microbalance and a massspectrometer. The results of these investigations indicated that ALDtype of film growth using (Et₃Si)₃Sb+CH₃OH could not be achieved in theF-120™ reactor.

A deposition experiment using (Et₃Si)₃Sb+H₂O was conducted at 150° C.After 2000 deposition cycles no film growth took place on soda lime ornative oxide SiO₂/Si. A similar experiment using (Et₃Si)₂Te+H₂O was alsounsuccessful.

Although (Et₃Si)₃Sb may react with water and alcohols at normal pressurein large quantities, ALD process conditions are apparently not suitablefor the growth to occur through these types of reactions. U.S. PatentPublication No. 2009-0191330 to Xiao discloses the synthesis of varioussilylantimony precursors. However, experiments only show reactingtris(trimethylsilyl)antimony with methanol in a flask. Our results showthat under ALD process conditions in a flow type reactor no film isformed using (Et₃Si)₃Sb and CH₃OH.

Precursors for ALD in Combination with Sb, As, Bi, and P PrecursorsDisclosed Herein

The precursors used for ALD in combination with the Sb, As, Bi, and Pprecursors disclosed herein includes precursors that will react on thesurface with the adsorbed Sb, As, Bi, and P precursors disclosed herein.A multi-component film, such as a Ge—Sb—Te film, may comprise multipledeposition cycles for different binary materials, such as in the case ofGST, using Ge—Te cycles, Sb—Te cycles, and optionally Sb depositioncycles. Such multi-component materials may contain other precursors thanprecursors described herein, which are not favorable to use directly inthe same cycle with the Sb, As, Bi, and P precursors disclosed herein,but are favorable to use in a multi-component material process in othercycles.

In some embodiments Sb, As, Bi, and P precursors disclosed herein areused in an ALD reaction with an other reactant that is not water,alcohol or ozone. In some embodiments the reactant used for ALD incombination with Sb, As, Bi, and P precursors disclosed herein is not anaminogermanium precursor, such as tetraminogermanium or anorganotellurium precursor. In some embodiments the other reactant to beused in combination with the Sb, As, Bi, and P precursors disclosedherein is not a chalcogenide precursor. In some embodiments theprecursors used for ALD in combination with the Sb, As, Bi, and Pprecursors disclosed herein do not contain plasma. In some embodimentsthe precursors used for ALD in combination with the Sb, As, Bi, and Pprecursors disclosed herein do not contain nitrogen. In some embodimentsthe other reactant to be used in combination with the Sb, As, Bi, and Pprecursors disclosed herein is not an alkoxide substituted precursor. Insome embodiments the other reactant to be used in combination with theSb, As, Bi, and P precursors disclosed herein is not an aminosubstituted precursor. In some embodiments the other reactant to be usedin combination with the Sb, As, Bi, and P precursors disclosed herein isnot an alkyl substituted precursor. In some embodiments the precursorsused for ALD in combination with the Sb, As, Bi, and P precursorsdisclosed herein are not reducing precursors, such as hydrogen,H₂/plasma, amine, imines, hydrazine, silane, silyl chalcogenide,germane, ammonia, alkane, alkene or alkyne. In some embodiments the Sb,As, Bi, and P precursors disclosed herein act as a reducing agent in anALD process. In some embodiments the precursor used for ALD incombination with the Sb, As, Bi, and P precursors disclosed herein is anoxidizing precursor, such as SbCl₃. In some embodiments the oxidizingprecursor does not contain oxygen. In preferred embodiments theoxidizing precursor is not alcohol, water, or ozone.

Any of the following metal precursors can be used in the various ALDprocesses disclosed herein.

In some embodiments the metal precursor is metal-organic ororganometallic precursor. In some embodiments the metal precursor is ametal-organic or organometallic precursor, which does not containnitrogen. In some embodiments the metal precursor is a halide precursor.In some embodiments the metal precursor is a halide precursor and doesnot contain any organic groups as ligands. In some embodiments the metalprecursor contains only fluorides or chlorides, preferably chlorides, asligands. In some embodiments the metal precursor is an adduct precursor.Adducts are not considered as a ligands and adducted precursor canorganic groups as adducts without having organic groups as ligands, forexample, here it is considered that GeCl₂-dioxane does not have anyorganic groups as ligands. Ligands are groups or atoms which aredirectly bonded with the center atom.

In some embodiments, the reactants are selected such that adehalosilylation reaction occurs between the reactants. In someembodiments a metal precursor is selected so that a dehalosilylationreaction occurs between the metal reactant and a Sb, As, Bi, or Pprecursor disclosed herein in an ALD processes. In some embodiments themetal precursor is selected so that a comproportionation reaction occursbetween the metal reactant and a Sb, As, Bi, or P precursor disclosedherein in an ALD process.

Preferred precursors include, but are not limited to metal halides,alkyls, alkoxides, amides, silylamides, amidinates, cyclopentadienyls,carboxylates, betadiketonates and betadiketoimines.

Preferred metals in metal precursors include, but are not limited to Ga,Al, Ge, Bi, Zn, Cu, In, Ag, Au, Pb, Cd, Hg, Sn, Co, Ni, Si. In somecases the preferred metal can possibly be rare earth or alkaline rareearth metal.

More preferred Sb precursors include, any of the Sb precursors describedherein and Sb halides, such as SbCl₃, SbBr₃ and SbI₃, Sb alkoxides, suchas Sb(OEt)₃ and Sb amides.

More preferred Ge precursors include Ge halides, such as GeCl₂ andGeBr₂, adducted derivatives of GeCl₂, GeF₂ and GeBr₂, such asGeCl₂-dioxane. Preferably the oxidation state of Ge is +II.

More preferred Al precursors include Al halides, such as AlCl₃, and Alalkyls, such as trimethylaluminum (TMA).

More preferred Bi precursors include Bi halides, such as BiCl₃.

More preferred Ga precursors include Ga halides, such as GaCl₃, and Gaalkyls, such as trimethylgallium (TMG).

More preferred Zn precursors include elemental Zn, Zn halides, such asZnCl₂, and alkyl zinc compounds such Zn(Et)₂ or Zn(Me)₂.

More preferred Cu compounds, include Cu carboxylates, such asCu(II)-pivalate, Cu halide, such as CuCl or CuCl₂, Cu betadiketonates,such as Cu(acac)₂ or Cu(thd)₂ and Cu-amidinates.

More preferred In compounds, include In halides, such as InCl₃ and Inalkyl compounds, such as In(CH₃)₃.

More preferred Pb compounds include Pb alkyls, such as tetraphenyl leadPh₄Pb or tetraethyl lead Et₄Pb.

More preferred Si precursors include Si halides, such as SiCl₄, andamino silanes

More preferred Sn precursors include Sn halides, such as SnCl₄.

More preferred Ni precursors include metalorganic Ni compounds, such asNi(acac)₂ or Ni(C_(P))₂.

More preferred Co precursors include metalorganic Co compounds, such asCo(acac)₂ or Co(thd)₂.

Precursors for ALD in Combination with N Precursors Disclosed Herein

Metal precursors can be used with the precursors comprising nitrogenthat are disclosed herein to deposit thin films comprising nitrogen.

In some embodiments the metal precursor does not comprise a transitionmetal i.e. a metal selected from Groups 3 through 12 according to theIUPAC. In some embodiments the metal precursor does not comprise Si orGe. In some embodiments the metal precursor comprises Al, B, Ga, In, Snor Pb.

In some embodiments the metal precursor is a metal-organic ororganometallic precursor. In some embodiments the metal precursor is ahalide precursor. In some embodiments the metal precursor is a halideprecursor and does not contain any organic groups as ligands. In someembodiments the metal precursor contains only fluorides or chlorides,preferably chlorides, as ligands. In some embodiments the metalprecursor is an adduct precursor.

Preferred precursors include, but are not limited to metal halides,alkyls, alkoxides, amides, silylamides, amidinates, cyclopentadienyls,carboxylates, betadiketonates and betadiketoimines, wherein the metal isnot a transition metal.

More preferred Al precursors include Al halides, such as AlCl₃, and Alalkyls, such as trimethylaluminum (TMA).

More preferred Ga precursors include Ga halides, such as GaCl₃, and Gaalkyls, such as trimethylgallium (TMG).

More preferred In compounds, include In halides, such as InCl₃ and Inalkyl compounds, such as In(CH₃)₃.

More preferred Pb compounds include Pb alkyls, such as tetraphenyl leadPh₄Pb or tetraethyl lead Et₄Pb.

More preferred Sn precursors include Sn halides, such as SnCl₄.

Te and Se Precursors for Atomic Layer Deposition

Te and Se precursors are disclosed in U.S. application Ser. No.12/429,133 filed Apr. 23, 2009 entitled “Synthesis and Use of Precursorsfor ALD of Tellurium and Selenium Thin Films”. The disclosure of whichis incorporated by reference herein in its entirety.

Any of the following precursors can be used in the various ALD processesdisclosed herein. In particular, precursors comprising Te and Se aredisclosed.

In some embodiments the Te or Se precursor has Te or Se bound to twosilicon atoms. For example it can have a general formula ofA(SiR¹R²R³)₂, wherein A is Te or Se and R¹, R², and R³ are alkyl groupscomprising one or more carbon atoms. The R¹, R², and R³ alkyl groups canbe selected independently of each other in each ligand based on thedesired physical properties of the precursor such as volatility, vaporpressure, toxicity, etc. In some embodiments, R¹, R² and/or R³ can behydrogen, alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R²,R³ can be any organic groups containing heteroatoms, such as N, O, F,Si, P, S, Cl, Br or I. In some embodiments R¹, R², R³ can be halogenatoms. In some embodiments the Te precursor is Te(SiMe₂ ^(t)Bu)₂ and theSe precursor is Se(SiMe₂ ^(t)Bu)₂. In other embodiments the precursor isTe(SiEt₃)₂, Te(SiMe₃)₂, Se(SiEt₃)₂ or Se(SiMe₃)₂. In more preferredembodiments the precursor has a Te—Si or Se—Si bond and most preferablySi—Te—Si or Si—Se—Si bond structure.

In some embodiments the Te or Se precursor has a general formula of[R¹R²R³X¹]₃—Si-A-Si—[X²R⁴R⁵R^(6]3), wherein A is Te or Se; and whereinR¹, R², R³, R⁴, R⁵ and R⁶, can be independently selected to be alkyl,hydrogen, alkenyl, alkynyl or aryl groups. In some embodiments, R¹, R²,R³, R⁴, R⁵ and R⁶ can be any organic groups containing also heteroatoms,such as N, O, F, Si, P, S, Cl, Br or I. In some embodiments R¹, R², R³,R⁴, R⁵ and R⁶ can be halogen atoms. In some embodiments X¹ and X² can beSi, N, or O. In some embodiments X¹ and X² are different elements. Inembodiments when X is Si then Si will be bound to three R groups, forexample [R¹R²R³Si]₃—Si-A-Si—[SiR⁴R⁵R⁶]₃. In embodiments when X is N thennitrogen will only be bound to two R groups ([R¹R²N]₃—Si-A-Si—[NR³R⁴]₃).In embodiments when X is O, the oxygen will only be bound to one Rgroup, for example [R¹—O]₃—Si-A-Si—[O—R²]₃. R¹, R², R³, R⁴, R⁵ and R⁶groups can be selected independently of each other in each ligand basedon the desired physical properties of the precursor such as volatility,vapor pressure, toxicity, etc

In some embodiments the Te or Se precursors is selected from the groupconsisting of: R¹R²R³Si—Si-A-Si—SiR⁴R⁵R⁶; R¹R²N—Si-A-Si—NR³R⁴;R¹—O—Si-A-Si—O—R²; or R¹R²Si-A-SiR³R⁴ with a double bond between siliconand one of the R groups. In other embodiments the Te or Se precursorcomprises: a ring or cyclical configuration comprising a Te or Se atomand multiple Si atoms; or comprises more than one Te atoms or more thanone Se atoms. In these embodiments A is Te or Se and R¹, R², R³, R⁴, R⁵and R⁶, are selected from the group consisting of alkyl, hydrogen,alkenyl, alkynyl, or aryl groups. In some embodiments the Te or Seprecursor is not A(SiR¹R²R³)₂.

In some embodiments the Te or Se precursor has a formula similar to theformulas described above, however the Si atom has a double bond to oneof the R groups in the ligand (e.g. A-Si═) wherein A is Te or Se. Forexample, a partial structure of the precursor formula is representedbelow:

In some embodiments the precursor contains multiple atoms of Si and Teor Se. For example, a partial structure of a precursor in one embodimentis represented below wherein A is Te or Se:

The Si atoms in the partial formula pictured above can also be bound toone or more R groups. In some embodiments, any of the R groups describedherein can be used.

In some embodiments the precursor contains a Si—Te—Si or Si—Se—Si bondstructure in a cyclical or ring structure. For example, a partialstructure of a precursor in one embodiment is represented below, whereinA is Te or Se.

The R group can comprise an alkyl, alkenyl, alkynyl, alkylsilyl,alkylamine or alkoxide group. In some embodiments the R group issubstituted or branched. In some embodiments the R group is notsubstituted and/or is not branched. The Si atoms in the partial formulapictured above can also be bound to one or more R groups. In someembodiments, any of the R groups described herein can be used.

Atomic Layer Deposition of Sb—Te

Methods for forming Sb—Te thin films using Te precursors are disclosedin U.S. application Ser. No. 12/429,133 filed Apr. 23, 2009 entitled“Synthesis and Use of Precursors for ALD of Tellurium and Selenium ThinFilms”. The disclosure of which is incorporated by reference herein inits entirety.

In some embodiments, Sb—Te, preferably Sb₂Te₃, films are deposited byALD preferably without the use of plasma, however in some cases plasmamight be used, if needed. For example, if elemental Te films or Te-richfilms are desired plasma, such as hydrogen plasma, hydrogen radicals oratomic hydrogen, may be used. Another use for plasma is doping of thefilms, for example doping by O, N or Si may be done using plasma.

According to some embodiments, an Sb₂Te₃ thin film is formed on asubstrate in a reaction chamber by an ALD type process comprisingmultiple Sb—Te deposition cycles, each deposition cycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a Sb        precursor into the reaction chamber to form no more than about a        single molecular layer of the Sb precursor on the substrate;    -   removing excess first reactant from the reaction chamber;    -   providing a second vapor phase reactant pulse comprising an Te        precursor to the reaction chamber such that the Te precursor        reacts with the Sb precursor on the substrate to form Sb₂Te₃;        and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber.

This can be referred to as the Sb—Te deposition cycle. Each Sb—Tedeposition cycle typically forms at most about one monolayer of Sb₂Te₃.In some embodiments, the Sb—Te deposition cycle is repeated until a filmof a desired thickness is formed.

Although the illustrated Sb—Te deposition cycle begins with provision ofthe Sb precursor, in other embodiments the deposition cycle begins withthe provision of the Te precursor.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of Te or Sbprecursor while continuing the flow of an inert carrier gas such asnitrogen or argon.

In some embodiments the Sb source is SbX₃, wherein X is a halogenelement. More preferably the Sb source is SbCl₃ or SbI₃.

Preferably, the Te precursor has a formula of Te(SiR¹R²R³)₂, wherein R¹,R², and R³ are alkyl groups comprising one or more carbon atoms. The R¹,R², and R³ alkyl groups can be selected based on the desired physicalproperties of the precursor such as volatility, vapor pressure,toxicity, etc. In some embodiments the Te precursor is Te(SiMe₂Bu)₂. Inother embodiments the precursor is Te(SiEt₃)₂ or Te(SiMe₃)₂. In someembodiments the Te precursor is Te(SiEt₃)₂ and the Sb precursor isSbCl₃.

In some embodiments, one or more dopants selected from the groupconsisting of O, N, C, Si, Sn, Ag, Al, Ga, P, Fe, Ge, In, Ag, Se, Te orBi, but not limited to those, is introduced into film. The precursorcomprising dopant reacts preferably, but not necessarily, with the Teprecursors described herein.

The particular process conditions can be selected by the skilled artisanbased on the properties of the selected precursors and desiredproperties of the deposited film.

Atomic Layer Deposition of Sb—Te Using Sb and Sb—Te Cycles

In some embodiments, Sb_(x)Te_(y) films having a desired composition canbe deposited using Sb and Sb—Te cycles.

The ratio of Sb—Te to the total number of cycles, e.g. number of Sbcycles and Sb—Te cycles, can be varied such that a Sb_(x)Te_(y) film isdeposited with a desired composition. The variables x and y can beexpressed as atomic ratios, atomic percentage, or the atomic compositionper molecule. The units of expression of x and y should be apparent tothe skilled artisan.

In some embodiments, the ratio of Sb cycles to Sb—Te cycles is betweenabout 1:100 and 100:1. Preferably, the ratio of Sb—Te cycles to Sb andSb—Te cycles is selected to deposit an Sb_(x)Te_(y) thin film having adesired composition. In some embodiments, Sb₂Te₃ is deposited.

In some embodiments, x is preferably between about 30% and about 50%. Insome embodiments, x preferably is between about 35% and 45%.

In some embodiments, y is preferably between about 50% and 70%. In someembodiments, y is preferably between about 55% and 65%.

In some embodiments x is preferably about 2. In some embodiments, y isbetween 0 and about 3. In some embodiments, x is 2 and y is 1. In someembodiments the Sb film is doped with Te and therefore the y is fromabout 1% to about 10% and x is from about 99% to 90%, respectively,

In some embodiments, the Sb—Te thin film is crystalline as deposited. Insome embodiments, the Sb—Te thin film can be amorphous as deposited. Insome embodiments, the thin film can be annealed to convert an amorphousthin film to a crystalline thin film.

In some embodiments, any of the process conditions described herein canbe used. For example, the reactants, reactant flow rates andconcentrations, temperature, etc. described herein can be used for theSb or Sb—Te deposition cycles.

In some embodiments, one or more dopants selected from the groupconsisting of O, N, C, Si, Sn, Ag, Al, Ga, P, Fe, Ge, In, Ag, Se, Te orBi, but not limited to those, is introduced into Sb—Te film. In someembodiments, the Sb—Te film is doped with Ag and In and have acomposition of approximately Ag_(0.055)In_(0.065)Sb_(0.59)Te_(0.29).

EXAMPLE 2

Sb_(x)Te_(y) films were grown using Sb deposition cycles and Sb₂Te₃deposition cycles. The substrate temperature was about 95° C. during thedeposition cycles. Sb₂Te₃ was deposited with SbCl₃ and Te(SiEt₃)₂ usinga deposition cycle comprising:

a 1 second SbCl₃ pulse;

a 2 second purge;

a 1 second Te(SiEt₃)₂ pulse; and

a 2 second purge.

Sb was deposited by a Sb deposition cycle with SbCl₃ and Sb(SiEt₃)₃comprising:

a 1 second SbCl₃ pulse;

a 2 second purge;

a 2 second Sb(SiEt₃)₃ pulse; and

a 2 second purge.

Films of different compositions were deposited while varying the ratioof Sb to Sb₂Te₃. The data is illustrated in FIGS. 5-7.

FIG. 5 shows the composition of the deposited films versus the ratio ofSb₂Te₃ cycles to the total number of Sb and Sb₂Te₃ cycles. Thecomposition of pure Sb and Sb₂Te₃ are indicated for reference on FIG. 5.FIG. 5 shows two linear regions with different slopes. The first regionhas a first slope for ratios from 0 to about 0.66. The slope changes forthe second linear region for cycle ratios from about 0.66 to 1. The datain FIG. 5 indicates that the composition of the deposited Sb—Te film canbe tailored based on the ratio of Sb cycles to Sb₂Te₃ cycles.

FIG. 6 illustrates the average growth rate per cycle versus the ratio ofSb₂Te₃ cycles to the total number of Sb and Sb₂Te₃ cycles. The averagegrowth rate for the Sb deposition cycle is about 0.45 Å/cycle. Theaverage growth rate for a Sb₂Te₃ deposition cycle is about 0.15 Å/cycle.FIG. 6 illustrates that the average growth rate per cycle approaches theSb₂Te₃ growth rate per cycle for a cycle ratio of about 0.66.

The crystallinity was also measured by GIXRD. FIG. 7 illustrates GIXRDdata for Sb—Te films of varying compositions, including Sb₇₀Te₃₀,Sb₈₃Te₁₇, and Sb₈₆Te₁₄. All three films illustrated in FIG. 7 werecrystalline. No chlorine was detected by EDX measurements of thedeposited films.

Atomic Layer Deposition of Ge—Sb

In some embodiments, a Ge_(x)Sb_(y) thin film is formed by ALD withoutthe use of plasma. FIG. 2 is a flow chart generally illustrating amethod for forming a Ge—Sb thin film 20 in accordance with oneembodiment. A Ge—Sb thin film is formed on a substrate by an ALD typeprocess comprising multiple Ge—Sb deposition cycles, each depositioncycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a Ge        precursor 21 into the reaction chamber to form no more than        about a single molecular layer of the Ge precursor on the        substrate;    -   removing excess first reactant from the reaction chamber 23;    -   providing a second vapor phase reactant pulse comprising a Sb        precursor 25 to the reaction chamber such that the Sb precursor        reacts with the Ge precursor on the substrate; and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber 27.

This can be referred to as the Ge—Sb deposition cycle. Each Ge—Sbdeposition cycle typically forms at most about one monolayer of Ge—Sb.The Ge—Sb deposition cycle is repeated until a film of a desiredthickness is formed 29. In some embodiments a Ge—Sb film of from about10 Å to about 2000 Å is formed.

The x and y values and composition of the Ge_(x)Sb_(y) film can vary. Insome embodiments, x and y are less than 1. In some embodiments, the sumof x and y is equal to about 1, or 100 if the x and y values areexpressed as a percentage.

Although the illustrated Ge—Sb deposition cycle begins with provision ofthe Ge precursor, in other embodiments the deposition cycle begins withthe provision of the Sb precursor.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of Ge or Sbprecursor while continuing the flow of an inert carrier gas such asnitrogen or argon.

Preferably, the Ge source is GeX₂ or GeX₄, wherein X is a halogenelement. Preferably the oxidation state of Ge is +II. In someembodiments the Ge source is GeBr₂. In some embodiments the Ge source isgermanium halide with coordinating ligands, such as dioxane ligands.Preferably the Ge source with coordinating ligands is germanium dihalidecomplex, more preferably a germanium dichloride dioxane complexGeCl₂.C₄H₈O₂.

The Sb precursor can be any of the Sb precursors described herein.Preferably, the second Sb precursor has a formula of Sb(SiR¹R²R³)₂,wherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected based on thedesired physical properties of the precursor such as volatility, vaporpressure, toxicity, etc.

The substrate temperature during forming the Ge—Sb thin film ispreferably less than 250° C. and more preferably less than 200° C. andeven more preferably below 100° C. If an amorphous thin film is desiredthe temperature can be lowered even further down to at or below about90° C. In some embodiments the deposition temperature can be below about80° C., below about 70° C., or even below about 60° C.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors.

The skilled artisan can determine the optimal reactant pulse timesthrough routine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited Ge—Sb thin film.

Preferably the Ge and Sb reactants are pulsed for about 0.05 to 10seconds, more preferably about 0.2 to 4 seconds, and most preferablyabout 1 to 4 seconds. The purge steps in which excess reactant andreaction by-products, if any, are removed are preferably about 0.05 to10 seconds, more preferably about 0.2-4 seconds, In some cases like inbatch ALD reactors the pulse and purge times can vary much more andlonger pulse times may be used even in order of minutes.

In some embodiments the deposited Ge—Sb thin films are amorphous. Insome embodiments, the deposited Ge—Sb thin films are crystalline.

In some embodiments, the deposited Ge—Sb film can be annealed.

In some embodiments, one or more dopants selected from the groupconsisting of O, N, C, Si, Sn, Ag, Al, Ga, P, Fe, Ge, In, Ag, Se, Te orBi, but not limited to those, is introduced into Ge—Sb film.

EXAMPLE 3

Ge—Sb films were deposited on substrates at approximately 95° C. usingSb(SiEt₃)₃ as the Sb source and GeCl₂.C₄H₈O₂ as the Ge source, using adeposition cycle comprising:

a 4 second GeCl₂.C₄H₈O₂ pulse;

a 6 second purge;

a 2 second Sb(SiEt₃)₃ pulse; and

a 2 second purge.

The growth rate per cycle was calculated at about 0.23 Å/cycle. X-raydiffractogram results indicated that the deposited film was amorphous.Energy dispersive x-ray (EDX) analysis showed that the deposited filmwas Ge_(0.82)Sb_(0.18) (82 at % Ge and 18 at % Sb).

Atomic Layer Deposition of Ge—Sb Using Sb and Ge—Sb Deposition Cycles

In some embodiments, Ge_(x)Sb_(y) films having a desired composition canbe deposited using Sb and Ge—Sb cycles.

The ratio of Ge—Sb to the total number of cycles, e.g. number of Sbcycles and Ge—Sb cycles, can be varied such that a Ge_(x)Sb_(y) film isdeposited with a desired composition. The variables x and y can beexpressed as atomic ratios, atomic percentage, or the atomic compositionper molecule. The units of expression of x and y should be apparent tothe skilled artisan.

In some embodiments, the ratio of Sb to Ge—Sb cycles is between about1:100 and 100:1. Preferably, the ratio of Sb to Sb and Ge—Sb is selectedto deposit a Ge—Sb thin film having a desired composition.

In some embodiments, x is preferably between about 5% and about 20%. Insome embodiments, y is preferably between about 80% and 95%. In oneembodiment, a film with eutectic composition, Ge₁₅Sb₈₅, is deposited. Insome embodiments the Sb film is doped with Ge and therefore the y isfrom about 1% to about 10% and x is from about 99% to 90%, respectively.

In some embodiments, the Ge—Sb thin film is crystalline as deposited. Insome embodiments, the Ge—Sb thin film can be amorphous as deposited. Insome embodiments, the thin film can be annealed to convert an amorphousthin film to a crystalline thin film.

In some embodiments, any of the process conditions described herein canbe used. For example, the reactants, reactant flow rates andconcentrations, temperature, etc. described herein can be used for theSb or Ge—Sb deposition cycles.

In some embodiments, one or more dopants selected from the groupconsisting of O, N, C, Si, Sn, Ag, Al, Ga, P, Fe, Ge, In, Ag, Se, Te orBi, but not limited to those, is introduced into film.

EXAMPLE 4

Ge—Sb films of varying compositions were deposited using Sb depositioncycles and Ge—Sb deposition cycles. The Sb was deposited by a Sbdeposition cycle using SbCl₃ and Sb(SiEt₃)₃ comprising:

a 1 second SbCl₃ pulse;

a 2 second purge;

a 2 second Sb(SiEt₃)₃ pulse; and

a 2 second purge.

The Ge—Sb films were deposited using Sb(SiEt₃)₃ as the Sb source andGeCl₂-C₄H₈O₂ as the Ge source, using a deposition cycle comprising:

a 4 second GeCl₂. C₄H₈O₂ pulse;

a 6 second purge;

a 2 second Sb(SiEt₃)₃ pulse; and

a 2 second purge.

FIGS. 8 and 9 illustrate composition and growth rate for the depositedGe—Sb films versus the ratio of Ge—Sb cycles to the total number ofcycles.

FIG. 8 illustrates a linear relationship between the ratios of Ge—Sbcycles to total number of cycles versus composition of the depositedfilm. FIG. 9 also illustrates a linear relationship between the averagegrowth rate per cycle and the ratio of Ge—Sb cycles to total cycles.

The Ge_(0.23)Sb_(0.77) and Ge_(0.82)Sb_(0.18) films were characterizedby EDX analysis. The Ge_(0.23)Sb_(0.77) and Ge_(0.82)Sb_(0.18) filmswere amorphous as deposited. EDX analysis also found that some chlorinewas present in the deposited Ge—Sb films. The amount of chlorineincreased with the amount of Ge present in the deposited film. It islikely that the chlorine comes from the GeCl₂-C₄H₈O₂ precursor. For PCMapplications with Ge—Sb films with relatively low Ge content (e.g.Ge_(0.15)Sb_(0.85)), the chlorine contribution from the GeCl₂-C₄H₈O₂precursor may not adversely affect device performance.

Atomic Layer Deposition of Ge—Sb—Te Using Sb, Sb—Te, Ge—Te and Ge—SbDeposition Cycles

According to some embodiments, Ge_(x)Sb_(y)Te_(z) (GST) thin films areformed on a substrate by an ALD type process comprising multipledeposition cycles.

In some embodiments Sb, Te and Ge deposition cycles are provided todeposit a GST thin film with a desired stoichiometry and desiredthickness. The particular ratio and order of cycles can be selected toachieve a thin film having a desired composition

In some embodiments Sb, Sb—Te, Ge—Te deposition cycles are provided todeposit a GST thin film with a desired stoichiometry and desiredthickness. The particular ratio and order of cycles can be selected toachieve the desired composition.

In some embodiments Sb, Sb—Te, Ge—Te and Ge—Sb deposition cycles areprovided to deposit a GST thin film with a desired stoichiometry anddesired thickness. The particular ratio and order of cycles can beselected to achieve the desired composition.

In some embodiments a GST thin film having the formula Ge₂Sb₂Te₅ isdeposited. In some embodiments, an Sb rich GST film, such as Ge₃Sb₆Te₅,is deposited. In some embodiments a thin film having the formulaGeSb₂Te₄ is deposited. In some embodiments a thin film having theformula GeSb₄Te₇ is deposited.

The skilled artisan will appreciate that the Sb, Sb—Te, Ge—Te and Ge—Sbdeposition cycles can be performed in any order. In some embodiments theGST deposition process begins with a Sb deposition cycle and in otherembodiments the GST deposition process begins with an Sb—Te depositioncycle, Ge—Te or Ge—Sb cycle.

The skilled artisan will also appreciate that multiple Sb depositioncycles can be performed consecutively prior to a Sb—Te or Ge—Sb cycle,multiple Sb—Te deposition cycles can be performed consecutively prior toa subsequent Sb or Ge—Sb deposition cycle, and multiple Ge—Sb depositioncycles can be performed consecutively prior to a subsequent Sb, Ge—Te orSb—Te deposition cycle.

In some embodiments, any of the process conditions described herein canbe used. For example, the reactants, reactant flow rates andconcentrations, temperature, etc. described herein can be used for theSb, Ge—Sb, Sb—Te, Ge—Te deposition cycles.

In some embodiments the GST thin film can be crystalline as deposited.In other embodiments an amorphous GST thin film is deposited. In someembodiments, the amorphous thin film can be annealed in the presence ofan inert gas, such as nitrogen. The substrate and thin film can also beheated during the annealing step at a temperature above the depositiontemperature. Preferably, the substrate temperature during the annealingstep is above about 130° C. More preferably, the substrate temperatureduring the annealing step is above about 250° C. Most preferably thetemperature during the annealing step is above 300° C. The annealingstep can change the crystallinity of the thin film. In some embodimentsan amorphous thin film can crystallize during the annealing step. Insome embodiments the crystallinity of a crystalline GST thin film canchange during the annealing step.

Atomic Layer Deposition of Ge—Sb—Se Using Sb, Sb—Se, Ge—Se and Ge—SbDeposition Cycles

According to some embodiments, Ge_(x)Sb_(y)Se_(z) thin films are formedon a substrate by an ALD type process comprising multiple depositioncycles.

In some embodiments Sb, Sb—Se, Ge—Se and Ge—Sb deposition cycles areprovided to deposit a thin film with a desired stoichiometry and desiredthickness. The particular ratio and order of cycles can be selected toachieve the desired composition.

The skilled artisan will appreciate that the Sb, Sb—Se, Ge—Se and Ge—Sbdeposition cycles can be performed in any order. In some embodiments thedeposition process begins with a Sb deposition cycle and in otherembodiments the deposition process begins with an Sb—Se depositioncycle, Ge—Se or Ge—Sb cycle.

The skilled artisan will also appreciate that multiple Sb depositioncycles can be performed consecutively prior to a Sb—Se or Ge—Sb cycle,multiple Sb—Se deposition cycles can be performed consecutively prior toa subsequent Sb or Ge—Sb deposition cycle, and multiple Ge—Sb depositioncycles can be performed consecutively prior to a subsequent Sb, Ge—Se orSb—Se deposition cycle.

In some embodiments, any of the process conditions described herein canbe used. For example, the reactants, reactant flow rates andconcentrations, temperature, etc. described herein can be used for theSb, Ge—Sb, Sb—Se, and Ge—Se deposition cycles.

In some embodiments the thin film can be crystalline as deposited. Inother embodiments an amorphous thin film is deposited. In someembodiments, the amorphous thin film can be annealed in the presence ofan inert gas, such as nitrogen. The substrate and thin film can also beheated during the annealing step at a temperature above the depositiontemperature. Preferably, the substrate temperature during the annealingstep is above about 130° C. More preferably, the substrate temperatureduring the annealing step is above about 250° C. Most preferably thetemperature during the annealing step is above 300° C. The annealingstep can change the crystallinity of the thin film. In some embodimentsan amorphous thin film can crystallize during the annealing step. Insome embodiments the crystallinity of a crystalline thin film can changeduring the annealing step.

Atomic Layer Deposition of Al—Sb

In some embodiments, a Al_(x)Sb_(y) thin film is formed by ALD withoutthe use of plasma. An Al—Sb thin film is formed on a substrate by an ALDtype process comprising multiple Al—Sb deposition cycles, eachdeposition cycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a Al        precursor into the reaction chamber to form no more than about a        single molecular layer of the Al precursor on the substrate;    -   removing excess first reactant from the reaction chamber;    -   providing a second vapor phase reactant pulse comprising a Sb        precursor to the reaction chamber such that the Sb precursor        reacts with the Al precursor on the substrate; and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber.

This can be referred to as the Al—Sb deposition cycle. Each Al—Sbdeposition cycle typically forms at most about one monolayer of Al—Sb.The Al—Sb deposition cycle is repeated until a film of a desiredthickness is formed. In some embodiments a Al—Sb film of from about 10 Åto about 2000 Å is formed.

The x and y values and composition of the Al_(x)Sb_(y) film can vary. Insome embodiments, x and y are less than 1. In some embodiments, the sumof x and y is equal to about 1, or 100 if the x and y values areexpressed as a percentage.

Although the illustrated Al—Sb deposition cycle begins with provision ofthe Al precursor, in other embodiments the deposition cycle begins withthe provision of the Sb precursor.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of Al or Sbprecursor while continuing the flow of an inert carrier gas such asnitrogen or argon.

Preferably, the Al source is AlX₃, wherein X is a halogen element. Insome embodiments the Al source is AlCl₃. In some embodiments Al sourceis aluminum alkyl compound, such as trimethylaluminum (TMA).

The Sb precursor can be any of the Sb precursors described herein.Preferably, the second Sb precursor has a formula of Sb(SiR'R²R³)₃,wherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected based on thedesired physical properties of the precursor such as volatility, vaporpressure, toxicity, etc.

The substrate temperature during forming the Al—Sb thin film ispreferably less than 500° C. and more preferably less than 350° C. andeven more preferably below 200° C. If an amorphous thin film is desiredthe temperature can be lowered even further down to at or below about90° C. In some embodiments the deposition temperature can be below about80° C., below about 70° C., or even below about 60° C.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors.

The skilled artisan can determine the optimal reactant pulse timesthrough routine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited Al—Sb thin film.

Preferably the Al and Sb reactants are pulsed for about 0.05 to 10seconds, more preferably about 0.2 to 4 seconds. The purge steps inwhich excess reactant and reaction by-products, if any, are removed arepreferably about 0.05 to 10 seconds, more preferably about 0.2-4seconds. In some cases like in batch ALD reactors the pulse and purgetimes can vary much more and longer pulse times may be used even inorder of minutes

In some embodiments the deposited Al—Sb thin films are amorphous. Insome embodiments, the deposited Al—Sb thin films are crystalline.

In some embodiments, the deposited Al—Sb film can be annealed.

Atomic Layer Deposition of In—Sb

In some embodiments, a In_(x)Sb_(y) thin film is formed by ALD withoutthe use of plasma. An In—Sb thin film is formed on a substrate by an ALDtype process comprising multiple In—Sb deposition cycles, eachdeposition cycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a In        precursor into the reaction chamber to form no more than about a        single molecular layer of the In precursor on the substrate;    -   removing excess first reactant from the reaction chamber;    -   providing a second vapor phase reactant pulse comprising a Sb        precursor to the reaction chamber such that the Sb precursor        reacts with the In precursor on the substrate; and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber.

This can be referred to as the In—Sb deposition cycle. Each In—Sbdeposition cycle typically forms at most about one monolayer of In—Sb.The In—Sb deposition cycle is repeated until a film of a desiredthickness is formed. In some embodiments a In—Sb film of from about 10 Åto about 2000 Å is formed.

The x and y values and composition of the In_(x)Sb_(y) film can vary. Insome embodiments, x and y are less than 1. In some embodiments, the sumof x and y is equal to about 1, or 100 if the x and y values areexpressed as a percentage.

Although the illustrated In—Sb deposition cycle begins with provision ofthe In precursor, in other embodiments the deposition cycle begins withthe provision of the Sb precursor.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of In or Sbprecursor while continuing the flow of an inert carrier gas such asnitrogen or argon.

Preferably, the In source is InX₃, wherein X is a halogen element. Insome embodiments the In source is InCl₃. In some embodiments In sourceis indium alkyl compound, such as trimethylindium (TMI). In someembodiments the In source is an indium betadiketonate, such as indiumacetylacetonate In(acac)₃. In some embodiment the In source is InCp or asubstituted Cp-derivative thereof.

The Sb precursor can be any of the Sb precursors described herein.Preferably, the second Sb precursor has a formula of Sb(SiR¹R²R³)₃,wherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected based on thedesired physical properties of the precursor such as volatility, vaporpressure, toxicity, etc.

The substrate temperature during forming the In—Sb thin film ispreferably less than 500° C. and more preferably less than 350° C. andeven more preferably below 200° C. If an amorphous thin film is desiredthe temperature can be lowered even further down to at or below about90° C. In some embodiments the deposition temperature can be below about80° C., below about 70° C., or even below about 60° C.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors.

The skilled artisan can determine the optimal reactant pulse timesthrough routine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited In—Sb thin film.

Preferably the In and Sb reactants are pulsed for about 0.05 to 10seconds, more preferably about 0.2 to 4 seconds. The purge steps inwhich excess reactant and reaction by-products, if any, are removed arepreferably about 0.05 to 10 seconds, more preferably about 0.2-4seconds. In some cases like in batch ALD reactors the pulse and purgetimes can vary much more and longer pulse times may be used even inorder of minutes.

In some embodiments the deposited In—Sb thin films are amorphous. Insome embodiments, the deposited In—Sb thin films are crystalline.

In some embodiments, the deposited In—Sb film can be annealed.

Atomic Layer Deposition of Ga—Sb

In some embodiments, a Ga_(x)Sb_(y) thin film is formed by ALD withoutthe use of plasma. An Ga—Sb thin film is formed on a substrate by an ALDtype process comprising multiple Ga—Sb deposition cycles, eachdeposition cycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a Ga        precursor into the reaction chamber to form no more than about a        single molecular layer of the Ga precursor on the substrate;    -   removing excess first reactant from the reaction chamber;    -   providing a second vapor phase reactant pulse comprising a Sb        precursor to the reaction chamber such that the Sb precursor        reacts with the Ga precursor on the substrate; and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber.

This can be referred to as the Ga—Sb deposition cycle. Each Ga—Sbdeposition cycle typically forms at most about one monolayer of Ga—Sb.The Ga—Sb deposition cycle is repeated until a film of a desiredthickness is formed. In some embodiments a Ga—Sb film of from about 10 Åto about 2000 Å is formed.

The x and y values and composition of the Ga_(x)Sb_(y) film can vary. Insome embodiments, x and y are less than 1. In some embodiments, the sumof x and y is equal to about 1, or 100 if the x and y values areexpressed as a percentage.

Although the illustrated Ga—Sb deposition cycle begins with provision ofthe Ga precursor, in other embodiments the deposition cycle begins withthe provision of the Sb precursor.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of Ga or Sbprecursor while continuing the flow of an inert carrier gas such asnitrogen or argon.

Preferably, the Ga source is GaX₃, wherein X is a halogen element. Insome embodiments the Ga source is GaCl₃. In some embodiments Ga sourceis gallium alkyl compound, such as trimethylgallium (TMG). In someembodiments the Ga source is a gallium betadiketonate.

The Sb precursor can be any of the Sb precursors described herein.Preferably, the second Sb precursor has a formula of Sb(SiR¹R²R³)₃,wherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected based on thedesired physical properties of the precursor such as volatility, vaporpressure, toxicity, etc.

The substrate temperature during forming the Ga—Sb thin film ispreferably less than 500° C. and more preferably less than 350° C. andeven more preferably below 200° C. If an amorphous thin film is desiredthe temperature can be lowered even further down to at or below about90° C. In some embodiments the deposition temperature can be below about80° C., below about 70° C., or even below about 60° C.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors.

The skilled artisan can determine the optimal reactant pulse timesthrough routine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited Ga—Sb thin film.

Preferably the Ga and Sb reactants are pulsed for about 0.05 to 10seconds, more preferably about 0.2 to 4 seconds. The purge steps inwhich excess reactant and reaction by-products, if any, are removed arepreferably about 0.05 to 10 seconds, more preferably about 0.2-4seconds. In some cases like in batch ALD reactors the pulse and purgetimes can vary much more and longer pulse times may be used even inorder of minutes.

In some embodiments the deposited Ga—Sb thin films are amorphous. Insome embodiments, the deposited Ga—Sb thin films are crystalline.

In some embodiments, the deposited Ga—Sb film can be annealed.

ALD Processes Using Sb Precursors for Depositing Materials Comprising Sband Co

Skutterudites such as CoSb₃, CeFe_(4−x)Co_(x)Sb₁₂ andLaFe_(4−x)Co_(x)Sb₁₂ have been studied for their potential use asthermoelectric materials.

In some embodiments, a thin film comprising Co and Sb is formed by ALDwithout the use of plasma. A thin film comprising Co and Sb is formed ona substrate by an ALD type process comprising multiple depositioncycles, each deposition cycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a Co        precursor into the reaction chamber to form no more than about a        single molecular layer of the Co precursor on the substrate;    -   removing excess first reactant from the reaction chamber;    -   providing a second vapor phase reactant pulse comprising a Co        precursor to the reaction chamber such that the Sb precursor        reacts with the Co precursor on the substrate; and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber.

This can be referred to as the Co—Sb deposition cycle. Each Co—Sbdeposition cycle typically forms at most about one monolayer of Co—Sb.The Co—Sb deposition cycle is repeated until a film of a desiredthickness is formed. In some embodiments a Co—Sb film of from about 10 Åto about 2000 Å is formed.

The x and y values and composition of the Co_(x)Sb_(y) film can vary. Insome embodiments, x and y are less than 1. In some embodiments, the sumof x and y is equal to about 1, or 100 if the x and y values areexpressed as a percentage.

Although the illustrated Co—Sb deposition cycle begins with provision ofthe Co precursor, in other embodiments the deposition cycle begins withthe provision of the Sb precursor.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of Sb or Coprecursor while continuing the flow of an inert carrier gas such asnitrogen or argon.

Preferably, the Co source is Co-amidinate or Co-betadiketonate, such asCo(acac)₂, Co(acac)₃, Co(thd)₂ or Co(thd)₃.

The Sb precursor can be any of the Sb precursors described herein.Preferably, the second Sb precursor has a formula of Sb(SiR¹R²R³)₃,wherein R², and R³ are alkyl groups comprising one or more carbon atoms.The R¹, R², and R³ alkyl groups can be selected based on the desiredphysical properties of the precursor such as volatility, vapor pressure,toxicity, etc.

Further materials or dopants that can be included in the Co—Sbdeposition cycles include transition metals such as Fe, La or Ce. Otherdopants selected from the group consisting of O, N, C, Si, Sn, Ag, Al,Ga, P, Fe, Ge, In, Ag, Se, Te or Bi, but not limited to those may alsobe introduced into film.

The substrate temperature during forming the Co—Sb thin film ispreferably less than 500° C. and more preferably less than 350° C. andeven more preferably below 200° C. If an amorphous thin film is desiredthe temperature can be lowered even further down to at or below about90° C. In some embodiments the deposition temperature can be below about80° C., below about 70° C., or even below about 60° C.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors.

The skilled artisan can determine the optimal reactant pulse timesthrough routine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited Co—Sb thin film.

Preferably the Co and Sb reactants are pulsed for about 0.05 to 10seconds, more preferably about 0.2 to 4 seconds. The purge steps inwhich excess reactant and reaction by-products, if any, are removed arepreferably about 0.05 to 10 seconds, more preferably about 0.2-4seconds. In some cases like in batch ALD reactors the pulse and purgetimes can vary much more and longer pulse times may be used even inorder of minutes.

In some embodiments the deposited Co—Sb thin films are amorphous. Insome embodiments, the deposited Co—Sb thin films are crystalline.

In some embodiments, the deposited Co—Sb film can be annealed.

ALD Processes Using Sb Precursors for Depositing Zn—Sb

Also ZnSb has also been studied for its potential use as athermoelectric material. In some embodiments, a thin film comprisingZn—Sb is formed by ALD without the use of plasma. An Zn—Sb thin film isformed on a substrate by an ALD type process comprising multiple Zn—Sbdeposition cycles, each deposition cycle comprising:

-   -   providing a first vapor phase reactant pulse comprising a Zn        precursor into the reaction chamber to form no more than about a        single molecular layer of the Zn precursor on the substrate;    -   removing excess first reactant from the reaction chamber;    -   providing a second vapor phase reactant pulse comprising a Zn        precursor to the reaction chamber such that the Sb precursor        reacts with the Zn precursor on the substrate; and    -   removing excess second reactant and reaction byproducts, if any,        from the reaction chamber.

This can be referred to as the Zn—Sb deposition cycle. Each Zn—Sbdeposition cycle typically forms at most about one monolayer of Zn—Sb.The Zn—Sb deposition cycle is repeated until a film of a desiredthickness is formed. In some embodiments a Zn—Sb film of from about 10 Åto about 2000 Å is formed.

The x and y values and composition of the Zn_(x)Sb_(y) film can vary. Insome embodiments, x and y are less than 1. In some embodiments, the sumof x and y is equal to about 1, or 100 if the x and y values areexpressed as a percentage.

Although the illustrated Zn—Sb deposition cycle begins with provision ofthe Zn precursor, in other embodiments the deposition cycle begins withthe provision of the Sb precursor.

In some embodiments, the reactants and reaction by-products can beremoved from the reaction chamber by stopping the flow of Zn or Sbprecursor while continuing the flow of an inert carrier gas such asnitrogen or argon.

Preferably, the Zn source is ZnX₂, wherein X is a halogen element. Insome embodiments the Zn source is ZnCl₂. In some embodiments Zn sourceis zinc alkyl compound, such as dimethylzinc or dimethylzinc.

The Sb precursor can be any of the Sb precursors described herein.Preferably, the second Sb precursor has a formula of Sb(SiR¹R²R³)₃,wherein R¹, R², and R³ are alkyl groups comprising one or more carbonatoms. The R¹, R², and R³ alkyl groups can be selected based on thedesired physical properties of the precursor such as volatility, vaporpressure, toxicity, etc.

The substrate temperature during forming the Zn—Sb thin film ispreferably less than 500° C. and more preferably less than 350° C. andeven more preferably below 200° C. If an amorphous thin film is desiredthe temperature can be lowered even further down to at or below about90° C. In some embodiments the deposition temperature can be below about80° C., below about 70° C., or even below about 60° C.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors.

The skilled artisan can determine the optimal reactant pulse timesthrough routine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited Zn—Sb thin film.

Preferably the Zn and Sb reactants are pulsed for about 0.05 to 10seconds, more preferably about 0.2 to 4 seconds. The purge steps inwhich excess reactant and reaction by-products, if any, are removed arepreferably about 0.05 to 10 seconds, more preferably about 0.2-4seconds. In some cases like in batch ALD reactors the pulse and purgetimes can vary much more and longer pulse times may be used even inorder of minutes.

In some embodiments the deposited Zn—Sb thin films are amorphous. Insome embodiments, the deposited Zn—Sb thin films are crystalline.

In some embodiments, the deposited Zn—Sb film can be annealed.

ALD Processes Using Group VA Precursors Comprising As, Bi, and P

In some embodiments, precursors comprising As, Bi, or P can besubstituted for any of the Sb precursors described herein. In someembodiments the As precursor is As(SiMe₂ ^(t)Bu)₃, As(SiEt₃)₃, orAs(SiMe₃)₃. In some embodiments the Bi precursor is Bi(SiMe₂ ^(t)Bu)₃,Bi(SiEt₃)₃, or Bi(SiMe₃)₃. In some embodiments the P precursor isP(SiMe₂ ^(t)Bu)₃, P(SiEt₃)₃, or P(SiMe₃)₃.

In some embodiments, thin films comprising As can be made including:As—Te, As—Se, In—As, Ga—As, In—Ga—As, As—S and Al—As. Any of theprecursors and compounds described herein can be used with the Asprecursors. In some preferred embodiments the As precursor is As(SiMe₂^(t)Bu)₃, As(SiEt₃)₃, or As(SiMe₃)₃.

In some embodiments, thin films comprising Bi can be made including:elemental Bi, Bi—Te, Bi—Se, In—Bi, Sb—Bi, Ga—Bi, and Al—Bi. Any of theprecursors and compounds described herein can be used with the Biprecursors. In some preferred embodiments the Bi precursor is Bi(SiMe₂^(t)Bu)₃, Bi(SiEt₃)₃, or Bi(SiMe₃)₃.

In some embodiments, thin films comprising P can be made including:P—Te, P—Se, In—P, Ga—P, Cu—P and Al—P. Any of the precursors andcompounds described herein can be used with the P precursors. In somepreferred embodiments the P precursor is P(SiMe₂ ^(t)Bu)₃, P(SiEt₃)₃, orP(SiMe₃)₃.

In some embodiments a Ga—As film is deposited using GaCl₃ and As(SiH₃)₃as precursors.

In some embodiments a film comprising a Group III-V compoundsemiconductor film is deposited having a formula of (M¹, M², M³)(A¹, A²,A³) i.e. M¹ _(x)M² _(y)M³ _(z)A¹ _(p)A² _(k)A³ _(l), where M's can beselected from Al, Ga or In and A's can be selected from P, As, Sb. Insome embodiments the Group III-V compound semiconductor film is aternary compound, such as (Ga, Al)As, Ga(As,Sb) or (Ga, In)As film. Insome embodiments the Group III-V compound semiconductor film is aquaternary compound film, such as a (Ga, In)(As, P) film or a (Al, In,Ga)P film.

EXAMPLE 5

Ga—As films were deposited using GaCl₃ and As(SiEt₃)₃ as precursors. 500cycles of Ga—As were used to deposit Ga—As on a silicon substrate withnative oxide. Reaction temperatures were 100° C. and 120° C. TheAs(SiEt₃)₃ source temperature was from about 50° C. to about 70° C. TheGaCl₃ was held at room temperature. Each Ga—As cycle was:

a 0.5 second GaCl₃ pulse;

a 2 second purge;

a 1 second As(SiEt₃)₃ pulse; and

a 2 second purge.

The Ga—As films were characterized by EDX analysis asGa_(0.58)As_(0.42). The growth rate for the Ga_(0.58)As_(0.42) filmswere approximately from about 0.5 Å/cycle to about 0.7 Å/cycle. EDXanalysis also found that some chlorine and oxygen was present in thedeposited Ga—As films. It is to be noted that these processes are notoptimized and therefore some impurities in the films are not uncommon.

ALD Processes Using Precursors Comprising N

In some embodiments, precursors comprising N can be substituted for theSb precursors described herein and used in the ALD cycles. In someembodiments the precursor comprising N is N(SiMe₂ ^(t)Bu)₃, N(SiH₃)₃,N(SiEt₃)₃, or N(SiMe₃)₃. In some embodiments the precursor comprising Nis N(SiMe₃)H. In some embodiments the precursor comprising N describedherein is not N(SiH₃)₃.

In some embodiments, the precursors comprising N can be used in an ALDcycle with a precursor comprising B, Al, Ga, or In to deposit a thinfilm including: B—N, Al—N, Ga—N and In—N.

In some embodiments a film comprising a Group III-V compoundsemiconductor film is deposited having a formula of (M¹, M², M³)N i.e.M¹ _(x)M² _(y)M³ _(z)N, where M's can be selected from Al, Ga or In. Insome embodiments the Group III-V compound semiconductor film comprises aternary compound, such as (Ga,In)N, Ga(N,P), (Ga,Al)N or (Al, In)N film.In some embodiments the Group III-V compound semiconductor filmcomprises a quaternary compound, such as (Ga,In)(N,P), (Ga, In)(As, N),(Al, In)(N, P) or (Al, In, Ga)N.

Nanolaminates

Controlling the composition of materials with three or more elements(ternary or higher) can be difficult. However, it is easier to controlthe composition of binary materials deposited by ALD.

In some embodiments, multiple ALD cycles can be used to deposit a firstfilm followed by multiple ALD cycles to form a second film having acomposition different from the first film. In some embodiments, two ormore cycles are used to deposit the first film. In some embodiments, twoor more cycles are used to deposit the second film.

The stoichiometry of the resulting film can be precisely controlled byvarying the ratio of the second cycles. The thickness of each depositedlayer can be controlled by selecting the number ALD cycles.

In some embodiments, multiple ALD cycles can be used to deposit about ananometer or more of the first or second film. In some embodiments,preferably about 1 to 6 nm of material is deposited.

In some embodiments, multiple first and second films are formed. Forexample, the first and second cycles can be alternated to formalternating thin films of the first and second films.

In some embodiments, three or more films with different compositions canbe used to form a film having a desired composition, crystal structure,and other physical properties.

The first and second films can be any of the materials described herein.Preferably, the deposited film can comprise one or more of: Sb, Sb—Te,GeTe, Ge—Sb—Te, Sb₂Te₃, Sb₂Te, Ge—Sb, Ge₂Sb₂Se₅, Bi—Te, Bi—Se, Zn—Te,ZnSe, CuInSe₂, and Cu(In,Ga)Se₂. In some embodiments, one or moredopants selected from the group consisting of O, N, C, Si, Sn, Ag, Al,Ga, P, Fe, Ge, In, Ag, Se, Te or Bi, but not limited to those, isintroduced into film.

In some embodiments, the thin film can comprise a dielectric material.In some embodiments, the dielectric material can comprise SiO₂, TiO₂,Al₂O₃, ZrO₂, and HfO₂. In some embodiments, a dielectric material can beformed in combination with the phase change materials disclosed herein.For example, in one embodiment, SiO₂ can be deposited with Ge—Sb—Te thinfilms. The use of a dielectric layer with a phase change material canmodify the crystallization temperatures, resistivity, stability andother characteristics of the deposited film.

Other deposition processes known in the art can also be used to depositthe nanolaminates materials, for example, CVD, RTCVD, etc.

In some embodiments, Sb—Te and Ge—Te cycles are used to depositalternating layers of Sb₂Te₃ and Ge—Te. The stoichiometry of theresulting film can be precisely controlled by varying the ratio of theSb—Te and Ge—Te cycles. The thickness of each deposited layer can becontrolled by selecting the number of Sb—Te and Ge—Te cycles.

In some embodiments, Sb, Sb—Te, and Ge—Te cycles are used to depositalternating layers of Sb, Sb₂Te₃, and Ge—Te.

In some embodiments, Sb—Se and Ge—Se cycles are used to depositalternating layers of Sb₂Se₃ and Ge—Se.

In some embodiments, Sb, Sb—Se, and Ge—Se cycles are used to depositalternating layers of Sb, Sb₂Se₃, and Ge—Se.

In some embodiments, the thin film is crystalline as deposited. In someembodiments, the thin film is amorphous as deposited.

In some embodiments, the thin film can be annealed in the presence of aninert gas, such as nitrogen. In some embodiments, annealing can modifythe crystal structure of the deposited thin film.

The nanolaminate thin films can have superior properties to bulk films.For example, a nanolaminate with 2-6 nm thick individual layers canexhibit lower programming currents and faster working times than a bulkGST film with the same total thickness.

EXAMPLE 6

GeTe/Sb₂Te₃ (GT/ST)—nanolaminate samples were prepared at 80° C. using1000 total applied cycles. The following cycle sequences were used: (A)250×(2GT+2ST), (B) 100×(5GT+5ST), (C) 50×(10GT+10ST), (D)10×(50GT+50ST), (E) 5×(100GT+100ST) and (F) 2×(250GT+250ST). A referenceGST film using a sequence 500×(GT+ST) was also prepared. As depositedfilms D, E and F were crystalline with the cubic structure. All otherfilms were amorphous. The composition was studied by EDX. FIG. 11 showsthe film composition as a function of the applied subcycles. It can beseen that the Sb content decreases and the Ge content increases as theamount of subcycles increases.

Resistivities of the nanolaminate samples as well as GeTe, Sb₂Te₃ andGST samples were measured after annealing at different temperaturesunder a N₂ flow (FIG. 12). The crystalline samples were already at ahigh conductivity state as expected. The amorphous nanolaminate samplescrystallized between 125-150° C. causing their resistivity to decrease4-5 orders of magnitude. The crystallization temperature of the GeTesample was between 150 and 175° C.

High temperature XRD (HTXRD) measurements to 405° C. under N₂ wereconducted for samples A-E. The cubic structure of samples D and E wasretained during the measurement. Initially amorphous samples A-C withthe smaller amounts of subcycles crystallized at 150° C. to the cubicphase and later on at 350° C. to the stable hexagonal phase (FIGS. 13aand 13b )

In conclusion, by use of nanolaminates the film composition, crystalstructure and resistivity can be tailored.

HTXRD measurements from room temperature to 405° C. of samples D (FIG.13a ) and C (FIG. 13b ). Scan numbers 1-20 represent heating from roomtemperature to 405° C. and 21-30 cooling down back to room temperature.

Group VA Precursor Synthesis

Methods are also provided for making some of the Group VA precursorsused in the ALD processes described herein. In some embodiments, thegroup VA element is As, Sb, Bi, or P. In some embodiments, precursorsare synthesized having a formula of L(SiR¹R²R³)₃, wherein L is As, Sb,Bi, or P and R¹, R², and R³ are preferably alkyl groups with one or morecarbon atoms. In some embodiments the Group VA precursor that issynthesized has a formula of L(SiMe₃)₃ and in other embodiments has aformula of L(SiEt₃)₃ with L being As, Sb, Bi, or P.

In particular, Sb precursors having a formula of Sb(SiR¹R²R³)₃, whereinR¹, R², and R³ are preferably alkyl groups with one or more carbonatoms, can be synthesized. In some embodiments the Sb precursor that issynthesized is Sb(SiMe₃)₃ and in other embodiments is Sb(SiEt₃)₃.

FIG. 10 is a flowchart generally illustrating methods for forming Sbprecursors. In some embodiments the process for making a Sb precursorcomprises:

forming a first product by reacting a Group IA metal with a compoundcomprising Sb, preferably elemental Sb; and

subsequently adding a second reactant comprising R¹R²R³SiX to the firstproduct, wherein R¹, R² and R³ are alkyl groups with one or more carbonatoms and X is a halogen atom, thereby forming Sb(SiR¹R²R³)₃.

In some embodiments, a Group IA elemental metal, such as Li, Na, K, etc.is combined with elemental Sb. Preferably, the Group IA element isprovided as a powder or flakes and the elemental Sb is provided as ametal powder.

In some embodiments, a solvent, preferably a hydrocarbon, eitheraromatic or non-aromatic compound, which has a suitable boiling point,such as tetrahydrofuran (THF, (CH₂)₄O), or dimethoxyethane (DME,CH₃OCH₂CH₂OCH₃) is added to the Group IA metal and Sb. Preferably,naphthalene (C₁₀H₈) is added to the mixture, for example it mightfacilitate the solubility of IA metal and therefore also to help reduceSb. In some embodiments, ammonia can be used to catalyze the reactioninstead of naphthalene. In some embodiments the solvent is toluene orxylene. In some embodiments the solvent is s ether, with suitableboiling point.

In some embodiments, the mixture is heated and a reflux condenser isused to reflux the solution under an inert gas, such as argon, untilcompletion of the reaction. A pressure vessel heated to a desiredtemperature can also be used instead of a reflux condenser. After adesired intermediate product is formed, the solution can be cooled down.

In some embodiments, a silicon containing compound is then added to themixture. Preferably, the silicon containing compound has a formula ofR¹R²R³SiX, wherein R¹, R², and R³ are preferably alkyl groups with oneor more carbon atoms and X is preferably a halogen atom. R¹, R², and R³can be chosen based on the desired precursor properties of the finalproduct, including vapor pressure, melting point, etc. In someembodiments R¹, R², and R³ can all be the same group. In otherembodiments, R¹, R², and R³ can all be different groups. In someembodiments, R¹, R², and R³ are all ethyl groups (Et). In someembodiments, R¹, R², and R³ are all methyl groups (Me). In otherembodiments R¹ and R² are methyl groups and R³ is a tertbutyl group (Me₂^(t)Bu). In some embodiments, X is Cl. In some preferred embodiments,the silicon containing compound has a formula of Et₃SiCl or Me₃SiCl.

The mixture is continuously stirred until the reaction is complete. Insome embodiments the mixture is refluxed or heated under inert gas untilcompletion of the reaction. After the reaction is substantiallycomplete, the final product is separated and isolated from any solvents,by-products, excess reactants, or any other compounds that are notdesired in the final product. The product can be a solid or liquid atstandard temperature and pressure.

Other methods can also be used to produce the Sb precursors. In someembodiments, (R₃Si)₃Sb compounds can be produced by reacting R₃SiH withSbR₃ compounds. In some embodiments, (SiR₃)₃Sb compounds can be producedby reacting R₃SiLi with SbCl₃ compounds.

EXAMPLE 7

Sb(SiMe₃)₃ was produced by the following process. First, 2.02 g ofsodium and was added to 200 ml of dry THF. 3.56 g of Sb powder and 0.1 g(5.47 mmol) of naphthalene were added to the sodium and THF mixture in a350 ml Schlenk bottle. The resultant mixture was stirred and refluxedfor 48 hours. The mixture was then cooled to room temperature.

Next, 9.55 g of Me₃SiCl was added to the mixture. The mixture wasstirred and refluxed for 48 hours. Vacuum was used to remove unreactedMe₃SiCl and solvent. 100 ml of toluene was added to the mixture tofacilitate filtering of the mixture. The toluene solution was thenfiltered. The filtrate including the product solvent and volatileimpurities were removed using a vacuum.

The recovered product weighed about 2.5 g resulting in a calculatedreaction efficiency of about 25%. The composition of the product wasverified to be Sb(SiMe₃)₃ by nuclear magnetic resonance (NMR) and massspectroscopy (MS). The Sb(SiMe₃)₂ produced had a boiling point of about88° C. at a pressure of 2 Torr.

EXAMPLE 8

Sb(SiEt₃)₃ was produced by a process similar to that described inExample 7. First, 0.45 g of lithium was added to 300 ml of dry THF alongwith 2.60 g of Sb powder and 0.1 g of naphthalene in a 350 ml Schlenkbottle. The resultant mixture was stirred and refluxed for 48 hours. Themixture was then cooled to room temperature.

Next, 9.68 g of Et₃SiCl was added to the mixture. The mixture wasrefluxed for 48 hours. Vacuum was used to remove unreacted Et₃SiCl andunreacted solvent. 100 ml of toluene was added to the mixture tofacilitate filtering of the mixture. The toluene solution was thenfiltered. The filtrate including the product solvent and volatileimpurities were removed using a vacuum.

The recovered product weighed about 0.5 g resulting in a calculatedreaction efficiency of about 5%. The composition of the product wasverified to be Sb(SiEt₃)₂ by nuclear magnetic resonance (NMR) and massspectroscopy (MS). The Sb(SiEt₃)₂ produced had a boiling point of about148-153° C. at a pressure of 1 Torr.

EXAMPLE 9

Sb(SiEt₃)₃ was produced by a process similar to that described inExample 7. First 4.2 g of sodium was added to 200 ml of dry DME(dimethoxyethane, CH₃OCH₂CH₂OCH₃) along with 7.4 g of Sb powder and 0.4g naphthalene in 600 ml Schlenk bottle. The resultant mixture wasstirred and refluxed for approximately 70 hours. The mixture was thencooled to room temperature.

Next 30.0 g of Et₃SiCl was added to the mixture. The mixture wasrefluxed for 96 hours. Vacuum was used to remove unreacted Et₃SiCl andsolvent. 100 ml of hexane was added to the mixture to facilitatefiltering of the mixture. The hexane solution was then filtered. Thefiltrate, including the product was then evaporated to dryness.

The recovered product weighed about 21.3 g giving a yield of 77.5%. Thecomposition of the product was verified to be Sb(SiEt₃)₃ by nuclearmagnetic resonance (NMR) and mass spectroscopy (MS). The Sb(SiEt₃)₃produced had a boiling point of about 150° C. at a pressure of 1 torr.

EXAMPLE 10

As(SiEt₃)₃ was produced by a process similar to that described inExample 7. First 0.86 g of sodium was added to 150 ml of dry DME(dimethoxyethane, CH₃OCH₂CH₂OCH₃) along with 0.89 g of As powder and 0.1g naphthalene in 350 ml Schlenk bottle. The resultant mixture wasstirred and refluxed for approximately 24 hours. The mixture was thencooled to −10° C.

Next 6.0 g of Et₃SiCl was added to the mixture. The mixture was refluxedfor 24 hours. Vacuum was used to remove unreacted Et₃SiCl and solvent.100 ml of hexane was added to the mixture to facilitate filtering of themixture. The hexane solution was then filtered. The filtrate includingthe product solvent and volatile impurities were removed using a vacuum.

The recovered product weighed about 2.8 g giving a yield of 56%. Thecomposition of the product was verified to be As(SiEt₃)₃ by nuclearmagnetic resonance (NMR) and mass spectroscopy (MS).

EXAMPLE 11

Bi(SiEt₃)₃ was produced by a process similar to that described inExample 7. First 0.76 g of sodium was added to 100 ml of thy DME(dimethoxyethane, CH₃OCH₂CH₂OCH₃) along with 2.31 g of Bi powder and 0.1g naphthalene in 350 ml Schlenk bottle. The resultant mixture wasstirred and refluxed for approximately 24 hours plus 4 days at roomtemperature. The mixture was then cooled to −10° C.

Next 5.25 g of Et₃SiCl was added to the mixture. The mixture wasrefluxed for 24 hours. Vacuum was used to remove unreacted Et₃SiCl andsolvent. 100 ml of hexane was added to the mixture to facilitatefiltering of the mixture. The hexane solution was then filtered. Thefiltrate including the product solvent and volatile impurities wereremoved using a vacuum.

The recovered product weighed about 3.2 g giving a yield of 52%. Thecomposition of the product was verified to be Bi(SiEt₃)₃ by nuclearmagnetic resonance (NMR) and mass spectroscopy (MS).

Precursors Comprising Group VA Elements and Synthesis

Precursors comprising As, Bi and P, such as (R₃Si)₃As, (R₃Si)₃P, and(R₃Si)₃Bi can also be synthesized using similar methods to thosedescribed here for Sb.

Methods for synthesizing precursors comprising N bonded to Sn can befound, for example from Sisido et al. Journal of Organic Chemistry(1964), 29(4), 907-9 and Lehn et al. Journal of the American ChemicalSociety (1964), 86(2), 305.

It will be appreciated by those skilled in the art that variousmodifications and changes can be made without departing from the scopeof the invention. Similar other modifications and changes are intendedto fall within the scope of the invention, as defined by the appendedclaims.

We claim:
 1. An atomic layer deposition (ALD) process for forming anitrogen-containing thin film on a substrate in a reaction chambercomprising a plurality of deposition cycles, each cycle comprising:providing a pulse of a first vapor phase halide reactant into thereaction chamber to form no more than about a single molecular layer ofthe reactant on the substrate, wherein the first vapor phase reactantdoes not comprise transition metal; removing excess first reactant fromthe reaction chamber; providing a pulse of a second vapor phase reactantto the reaction chamber such that the second vapor phase reactant reactsdirectly with the first halide reactant on the substrate to form anitrogen containing thin film, wherein the second vapor phase reactantcomprises N(AR¹R²R³)_(x)R_(3−x), and wherein x is from 1 to 3, A is Si,Ge or Sn, and R, R¹, R², and R³ can be independently selected to belinear, cyclic, branched or substituted alkyl, hydrogen or aryl groups;and removing excess second reactant and reaction byproducts, if any,from the reaction chamber, wherein the nitrogen containing thin film isBN, AlN, GaN or InN.
 2. The process of claim 1, wherein x is 2, A is Siand R is hydrogen.
 3. The process of claim 1, wherein the second vaporphase reactant has a formula of N(SiR¹R²R³)_(x)R_(3−x).
 4. The processof claim 1, wherein the second vapor phase reactant is N(SiH₃)₃.
 5. Theprocess of claim 1, wherein the second vapor phase reactant is notN(SiH₃)₃.
 6. The process of claim 1, wherein the first vapor phasereactant is GaCl₃ or InCl₃.
 7. An atomic layer deposition (ALD) processfor forming a thin film comprising a group VA element on a substrate ina reaction chamber, the process comprising a plurality of Group VAelement deposition cycles, wherein each of the Group VA elementdeposition cycles comprise: providing a pulse of a first vapor phasehalide reactant into the reaction chamber to form no more than about asingle molecular layer of the reactant on the substrate; removing excessfirst reactant from the reaction chamber; providing a pulse of a secondvapor phase reactant to the reaction chamber such that the second vaporphase reactant reacts directly with the first halide reactant on thesubstrate to form a thin film comprising a group VA element, wherein thesecond vapor phase reactant comprises a group VA atom that is bonded toone or more of Si, Ge, or Sn, wherein the group VA element is Sb; andremoving excess second reactant and reaction byproducts, if any, fromthe reaction chamber.
 8. The method of claim 7, wherein the first vaporphase reactant is GeBr₂, GeCl₂—C₄H₈O₂, SbCl₃, GaCl₃, or InCl₃.
 9. Themethod of claim 7, wherein the first vapor phase reactant comprisesantimony.
 10. The method of claim 7, wherein the second vapor phasereactant is Sb(SiEt₃)₃.
 11. The method of claim 7, wherein the secondvapor phase reactant is Sb(SiMe₃)₃.
 12. The method of claim 7, whereinthe second vapor phase reactant comprises Sb(GeR¹R²R³)₃, wherein R¹, R²,and R³ are alkyl groups with one or more carbon atoms, wherein a Sbcontaining thin film is formed.
 13. The method of claim 7, wherein thesecond vapor phase reactant comprises Sb(SiR¹R²R³)₃, wherein R¹, R², andR³ are alkyl groups with one or more carbon atoms.
 14. The method ofclaim 7, wherein the first vapor phase reactant is not an aminogermaniumor organotellurium precursor or a reducing reactant or a plasmareactant.
 15. The method of claim 7, wherein the second vapor phasereactant comprises a group VA atom that is bonded to Si.
 16. The methodof claim 7, wherein the second vapor phase reactant comprises a group VAatom that is bonded to Ge.
 17. The method of claim 7, wherein the secondvapor phase reactant comprises a group VA atom that is bonded to Sn. 18.The method of claim 7, wherein the temperature of the substrate duringthe providing steps is below about 150° C.
 19. The method of claim 7,further comprising a Sb—Te deposition cycle comprising: providing afirst vapor phase reactant pulse comprising a Sb precursor into thereaction chamber to form no more than about a single molecular layer ofthe removing excess first reactant from the reaction chamber; providinga second vapor phase reactant pulse comprising a Te precursor to thereaction chamber such that the Te precursor reacts with the Sb precursoron the substrate, wherein the Te precursor has the formulaTe(SiR¹R²R³)₂, wherein R¹, R², and R³ are alkyl groups; and removingexcess second reactant and reaction byproducts, if any, from thereaction chamber.
 20. The method of claim 7, further comprising a Ge—Sbdeposition cycle comprising: providing a first vapor phase reactantpulse comprising a Ge precursor into the reaction chamber to form nomore than about a single molecular layer of the Ge precursor on thesubstrate; removing excess first reactant from the reaction chamber;providing a second vapor phase reactant pulse comprising an Sb precursorcomprising to the reaction chamber such that the Sb precursor reactswith the Ge precursor on the substrate; and removing excess secondreactant and reaction byproducts, if any, from the reaction chamber. 21.The method of claim 7, further comprising: a plurality of Te containingdeposition cycles, each cycle comprising alternate and sequential pulsesof a third vapor phase reactant and a fourth vapor phase reactantcomprising Te; and a plurality of Ge containing deposition cycles, eachcycle comprising alternate and sequential pulses of a fifth vapor phasereactant and a sixth vapor phase reactant comprising Ge, wherein aGe—Sb—Te thin film is formed on a substrate .
 22. The method of claim21, wherein the first reactant is an antimony halide, the third reactantis an antimony halide, the sixth reactant comprising Ge is a germaniumhalide and the fourth reactant comprising Te comprises Te(SiR¹R²R³)₂,wherein R₁ , R², and R³ are alkyl groups with one or more carbon atoms.23. The method of claim 7, further comprising: a plurality of Secontaining deposition cycles, each cycle comprising alternate andsequential pulses of a third vapor phase reactant and a fourth vaporphase reactant comprising Se; and a plurality of Ge containingdeposition cycles, each cycle comprising alternate and sequential pulsesof a fifth vapor phase reactant and a sixth vapor phase reactantcomprising Ge, wherein a Ge—Sb—Se thin film is formed on a substrate.24. The method of claim 7, further comprising: a second deposition cyclecomprising alternate and sequential pulses of a third vapor phasereactant and a fourth vapor phase reactant, the fourth vapor phasereactant comprising A(SiR¹R²R³)_(x), wherein R¹, R², and R³are alkylgroups with one or more carbon atoms and A is Sb, Te, or Se, and whereinx is 3 when A is Sb and x is 2 when A is Te or Se, wherein ananolaminate film is deposited.
 25. An atomic layer deposition (ALD)process for forming a thin film comprising a group VA element on asubstrate in a reaction chamber, the process comprising a plurality ofGroup VA element deposition cycles, wherein each of the Group VA elementdeposition cycles comprise: providing a pulse of a first vapor phasereactant into the reaction chamber to form no more than about a singlemolecular layer of the reactant on the substrate; removing excess firstreactant from the reaction chamber; providing a pulse of a second vaporphase reactant to the reaction chamber such that the second vapor phasereactant reacts with the first reactant on the substrate to form a thinfilm comprising a group VA element, wherein the second vapor phasereactant comprises As(SiR¹R²R³)₃, wherein R¹, R², and R³ are alkylgroups with one or more carbon atoms.
 26. The method of claim 25,wherein the first vapor phase reactant comprises gallium.